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GreyNoise has observed active exploitation attempts against CVE-2025-5777 (CitrixBleed 2), a memory overread vulnerability in Citrix NetScaler. Exploitation began on June 23 — nearly two weeks before a public proof-of-concept (PoC) was released on July 4.
We created a tag on July 7 to track this activity. Because GreyNoise retroactively associates pre-tag traffic with new tags, prior exploitation attempts are now visible in the GreyNoise Visualizer.
Key Observations
First observed activity: June 23, 2025
PoC released: July 4, 2025
GreyNoise tag published: July 7, 2025
CISA confirms activity with GreyNoise: July 9, 2025 (prior to KEV addition)
Early exploitation attempts came from malicious IPs geolocated in China. Rather than exploiting indiscriminately, these IPs targeted GreyNoise sensors configured to emulate Citrix NetScaler appliances, suggesting deliberate targeting.
CISA Confirmation
On July 9, shortly after we published the tag, CISA contacted GreyNoise to confirm exploitation activity. CVE-2025-5777 was subsequently added to the Known Exploited Vulnerabilities (KEV) catalog.
Recommended Actions
Defenders can dynamically block malicious IPs to reduce exposure and suppress alerts.
The above list will stay updated as new IPs are observed attempting to exploit CVE-2025-5777.
GreyNoise is developing an enhanced dynamic IP blocklist to help defenders take faster action on emerging threats. Click here to learn more or get on the waitlist.
— — —
Stone is Head of Content at GreyNoise Intelligence, where he leads strategic content initiatives that illuminate the complexities of internet noise and threat intelligence. In past roles, he led partnered research initiatives with Google and the U.S. Department of Homeland Security. With a background in finance, technology, and engagement with the United Nations on global topics, Stone brings a multidimensional perspective to cybersecurity. He is also affiliated with the Council on Foreign Relations.
Diverse Set of IPs Exploiting Atlassian Vulnerabilities, Not Just a Few Bad Actors.
At GreyNoise, we focus heavily on analyzing data trends and anomalies, as they form a fundamental part of our business. While we collect a vast amount of data regarding unsolicited packets being transmitted across the internet, it is only meaningful if we look at the bigger picture.
We have recently introduced some changes to our back-end system for calculating the trending and anomalous events we update hourly here. This has already proven beneficial, as it helped us detect a sudden increase in malicious Atlassian exploitation attempts late last week (gee, I wonder why…).
Atlassian-related topics occupy seven out of the top ten trending tag anomalies at the time of this writing.
We conducted an analysis on the various spikes and attempted to determine if they were all caused by the same few IPs searching for all possible vulnerabilities. However, our findings suggest a fair distribution of IPs trying to exploit different vulnerabilities. After examining data from the past 24 hours, we found that the highest number of overlapping IPs across all the tags mentioned above was only 9, with 67% of the total IPs seen only once.
As the year ends, ensure your Atlassian products are secure by removing them from the public internet and keeping them up to date. If they’re still unpatched, it likely is too late to avoid compromise. For extra measure, use our dynamic IP blocking feature to protect your organization from opportunistic mass exploitation.
Over at the GreyNoise Labs Grimoire, Ron Bowes has a new, deep-dive post out on the creation of a simple clone of the F5 BIG-IP management port to attract traffic and analyze it. Ron deployed the honeypot for a couple of weeks and then analyzed the traffic using tshark.
Some interesting findings include:
Brute-force attacks on the login page with basic credentials like “user123” and “password123”.
Attempts to exploit CVE-2021-22986, an SSRF issue in the authentication parser.
Traffic targeting the “/mgmt/tm/util/bash” endpoint, which is typically targeted for auth-bypass issues like CVE-2022-1388.
Two instances of exploitation attempts targeting the “/mgmt/shared/iapp/rpm-spec-creator endpoint”, which is related to CVE-2022-41800, an authenticated remote code execution vulnerability.
Ron does note that the majority of the traffic is not related to a rumored 0-day exploit, and that the honeypot helped provide insights into various attack attempts and vulnerabilities.
Pour out your fav caffeinated beverage and sink into Ron's insightful post!
CVE-2022-28958 was initially reported as a remote code execution (RCE) vulnerability in the D-Link DIR816L_FW206b01 firmware via the value parameter at shareport.php. This vulnerability, if real, would have posed a significant security risk, allowing unauthorized remote users to execute arbitrary code on the affected device.
However, further investigation into CVE-2022-28958 revealed that the vulnerability did not actually exist. Tests conducted on various firmware versions, including the reportedly vulnerable version 2.06b1, found no evidence of the vulnerability. Moreover, the original researcher who reported the vulnerability did not provide supporting evidence.
The CVE has been marked as REJECTED by the CVE List, retracted by the Certified Naming Authority that originally vetted and published the CVE, and CISA has removed the vulnerability from their catalog of known exploited vulnerabilities.
In response to these findings, GreyNoise researchers made the call to pull their D-Link DIR-816 tag for CVE-2022-28958. This action aligns with GreyNoise's commitment to providing the cybersecurity community with accurate and reliable threat intelligence.
The case of CVE-2022-28958 serves as a reminder of the importance of thorough and rigorous vulnerability verification. Incorrectly reported vulnerabilities can lead to unnecessary alarm and resource allocation in the cybersecurity community. They can also undermine trust in the reporting and cataloging systems that are crucial for effective vulnerability management.
In this context, the work of organizations like GreyNoise Intelligence and CISA is invaluable. By investigating reported vulnerabilities and making informed decisions based on their findings, they help ensure that the cybersecurity community can focus its efforts on real and present threats.
Have you heard of CVE-2023-49105? While the 10/10 CVE-2023-49103 got all the attention last week, organizations should not quickly overlook CVE-2023-49105!
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Last week, GreyNoise published a high-level and deep-dive blog into a seemingly simple (but actually complex) vulnerability in ownCloud (CVE-2023-49103) that permitted users to enumerate environmental variables. Since it was listed as CVSS 10/10, everybody jumped on it.
Once we understood the 10/10 vulnerability, CVE-2023-49103, we shifted focus to the 9.8/10 vulnerability, CVE-2023-49105, a WebDAV Api Authentication Bypass in ownCloud.
What we found is that CVE-2023-49105 is arguably a more severe vulnerability. Ron Bowes, Lead Security Researcher, quickly developed a PoC for this vulnerability (another deep-dive here!) and verified the findings published by Abionics Security’s write-up demonstrating how this vulnerability can enable remote code execution.
CVE-2023-49105 is an authentication bypass issue affecting ownCloud from version 10.6.0 to version 10.13.0. It allows an attacker to access, modify, or delete any file without authentication if the username is known. Even if the user has no signing key configured, ownCloud accepts pre-signed URLs, enabling the attacker to generate URLs for arbitrary file operations.
Successfully exploiting CVE-2023-49105 can lead to serious impacts like data theft, ransomware deployment, and remote code execution. While it may have received less initial attention than the CVSS 10 issue, organizations using affected ownCloud versions should treat patching this vulnerability as a critical priority. Unlike the CVSS 10 issue, this affects *all* installations, not just Docker-based ones.
Upgrading to ownCloud 10.13.3 or later is reported to resolve CVE-2023-49105.
Ron Bowes of the GreyNoise Labs team has made some updates to the deep dive into this critical vulnerability in ownCloud’s Graph API.
2023-11-29 UPDATE
Ron Bowes of the GreyNoise Labs team has put together a deep dive into this critical vulnerability in ownCloud’s Graph API. Ron discusses the exploit, its impact on Docker installations, and our comprehensive testing process, here at GreyNoise.
2023-11-27 ORIGINAL POST
On November 21, 2023, ownCloud publicly disclosed a critical vulnerability with a CVSS severity rating of 10 out of 10. This vulnerability, tracked as CVE-2023-49103, affects the "graphapi" app used in ownCloud.
ownCloud is a file server and collaboration platform that enables secure storage, sharing, and synchronization of commonly sensitive files.
The vulnerability allows attackers to access admin passwords, mail server credentials, and license keys.
GreyNoise has observed mass exploitation of this vulnerability in the wild as early as November 25, 2023.
The vulnerability arises from a flaw in the "graphapi" app, present in ownCloud versions 0.2.0 to 0.3.0. This app utilizes a third-party library that will reveal sensitive PHP environment configurations, including passwords and keys. Disabling the app does not entirely resolve the issue, and even non-containerized ownCloud instances are at risk. Docker containers before February 2023 are not affected.
Mitigation information listed in the vendor's disclosure includes manual efforts such as deleting a directory and changing any secrets that may have been accessed.
In addition to CVE-2023-49103, ownCloud has also disclosed other critical vulnerabilities, including an authentication bypass flaw (CVE-2023-49105) and a critical flaw related to the oauth2 app (CVE-2023-49104).
Organizations using ownCloud should address these vulnerabilities immediately.
CVE-2023-29552 is a high-severity vulnerability discovered in the Service Location Protocol (SLP), a legacy Internet protocol. This vulnerability allows an unauthenticated, remote attacker to register arbitrary services, enabling them to launch a Denial-of-Service (DoS) attack via a reflection amplification attack. BitSight first alerted the world to this weakness back in May.
The potential harm from this vulnerability is significant.Successful exploitation could potentially allow an attacker to launch one of the most powerful DoS amplification attacks in history, with an amplification factor as high as 2,200 times. This means that an attacker could send a small amount of traffic to a vulnerable SLP instance, which would then respond with a much larger amount of traffic to the victim's server. This could overwhelm the server, causing it to become unresponsive and disrupting the services it provides.
BitSight has noted that vulnerability affects more than 2,000 global organizations and over 54,000 SLP instances accessible via the internet, including VMWare ESXi Hypervisor, Konica Minolta printers, Planex Routers, IBM Integrated Management Module (IMM), SMC IPMI, and 665 other product types. This wide impact means that a large number of systems and services could potentially be disrupted by an attack exploiting this vulnerability.
The potential harms from this vulnerability are not limited to service disruption. DoS attacks can also lead to financial losses, especially for organizations that rely on web-based transactions. For instance, an online retailer could lose sales if their website becomes unavailable due to a DoS attack; or, financial services firms may be unable to process customer orb2b transactions. Furthermore, the recovery from such an attack could require significant resources, further increasing the financial impact.
Given the severity and potential impacts of this vulnerability, it's crucial for organizations to take steps to mitigate it.This could include upgrading to a release line that is not impacted by the vulnerability, or implementing other appropriate security measures to safeguard their networks and servers.
For Your Consideration
Folks may remember the recent HTTP/2 Rapid Reset vulnerability announced by Cloudflare. It was a zero-day vulnerability that exploited a weakness in the HTTP/2 protocol to generate massive Distributed Denial of Service (DDoS) attacks. The vulnerability, CVE-2023-44487, takes advantage of the ability of HTTP/2 to allow for multiple distinct logical connections to be multiplexed over a single HTTP session, with the rapid reset attack consisting of multiple HTTP/2 connections with requests and resets in rapid succession.
While both the Rapid Reset vulnerability and this new SLP vulnerability can lead to large-scale DDoS attacks, they exploit different protocols and mechanisms. The HTTP/2 Rapid Reset vulnerability exploits a feature in the HTTP/2 protocol to generate massive DDoS attacks, while the SLP amplification attack vector leverages the SLP protocol to amplify the volume of DDoS attacks.
We're Here To Help
GreyNoise customers can use our hourly updated blocklists for the SLP tag (compatible with Palo Alto, Cisco, Fortinet, and other next-gen firewalls) to gain proactive protection from non-benign sources looking for potential system with SLP exposed.
Citrix's NetScaler ADC and NetScaler Gateway have, once more, been found to have multiple vulnerabilities, tracked as CVE-2023-4966 and CVE-2023-4967.
On October 23, 2023, GreyNoise Detection Engineers added tag coverage for CVE-2023-4966, which is an information disclosure vulnerability in NetScaler ADC and NetScaler Gateway. When configured as a gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or as an AAA virtual server, an unauthenticated attacker could exploit the device in order to hijack an existing authenticated session. Depending on the permissions of the account they have hijacked, this could allow the attacker to gain additional access within a target environment and collect other account credentials.
CVE-2023-4967 is a denial-of-service (DoS) vulnerability that can potentially enable DoS attacks on vulnerable devices.
Both CVEs were published on October 10, 2023, and the tag for CVE-2023-4966 joins 11 other Citrix-specific tags in the GreyNoise tag corpus.
The GreyNoise Storm⚡Watch webcast/podcast provided extensive coverage of this vulnerability in this week’s episode.
Widespread Attacks
As of this post’s publish time, GreyNoise has observed just under seventy IP addresses attempting to exploit this vulnerability:
Activity started on the 24th and shows no signs of stopping.
Mitigating Harm
Citrix has urged customers to install updated versions of the affected devices as soon as possible. The recommended versions to upgrade to are NetScaler ADC and NetScaler Gateway 14.1-8.50 and later, NetScaler ADC and NetScaler Gateway 13.1-49.15 and later releases of 13.1, NetScaler ADC and NetScaler Gateway 13.0-92.19 and later releases of 13.0, NetScaler ADC 13.1-FIPS 13.1-37.164 and later releases of 13.1-FIPS, NetScaler ADC 12.1-FIPS 12.1-55.300 and later releases of 12.1-FIPS, and NetScaler ADC 12.1-NDcPP 12.1-55.300 and later releases of 12.1-NDcPP.
Remote access technologies are prime targets for attackers, especially when proof-of-concept code becomes available. GreyNoise Detection Engineers work with research partners, and conducts bespoke vulnerability research to provide timely access to real-time intelligence that can help your organization buy time to patch, remove the noise of opportunistic attackers, and give you the opportunity to focus on fending off targeted attacks.
Cisco Talos has updated their advisory to include a new CVE, CVE-2023-20273, "that is exploited to deploy the implant" with a fix estimated to be released on October 22nd. The Cisco Security Advisory was also updated to include the new CVE, information about observed attacks, mitigation, and Snort rule IDs.
We have also updated our illustration (below) to include the new CVE.
Original Post
On October 16th, 2023, Cisco disclosed a critical software Web UI Privilege Escalation Vulnerability under the identifier CVE-2023-20198 with a CVSS base score of 10. Cisco notes that the vulnerability has been exploited in the wild. The vulnerability allows an unauthenticated attacker to create an account with “privilege level 15 access” (full access to all commands). There is no patch for the privilege escalation vulnerability at the time of writing.
Initial Disclosure
In coordination with this disclosure, Cisco Talos published a threat advisory noting that the privilege escalation vulnerability CVE-2023-20198 is leveraged for initial access. Following this activity, an implant is delivered through a “yet undetermined mechanism” for which no patch is available.
“Leveraging existing detections, we observed the actor exploiting CVE-2021-1435, for which Cisco provided a patch in 2021, to install the implant after gaining access to the device. We have also seen devices fully patched against CVE-2021-1435 getting the implant successfully installed through an as-of-yet undetermined mechanism.”
Later in the threat advisory, the Snort intrusion detection system rule ID 3:50118:2 is called out as a way to address “this” threat.
The Snort rule 3:50118:2 "SERVER-WEBAPP Cisco IOS XE Web UI command injection attempt” does not include any mention that it detects CVE-2021-1435. In the rule’s references section, CVE-2019-12650 and CVE-2019-1862 — both command injection vulnerabilities — are mentioned via the following links:
If Snort rule 3:50118:2 detects the command injection vulnerabilities (CVE-2019-1862 / CVE-2019-12650 / CVE-2021-1435?) and the malicious implant in this recent string of attacks is installed through a “yet undetermined mechanism” on systems that are fully patched against CVE-2021-1435, then the vulnerability being leveraged to install the implant is not CVE-2021-1435. Additionally, a patch is available for CVE-2021-1435 whereas a patch is not available for the mechanism used to install the implant.
Surveying The Carnage
Further research by VulnCheck has demonstrated that systems affected by the malicious implants can be coerced to disclose their 18-character hexadecimal unique implant identifier.
Cisco buried the lede by not mentioning thousands of internet-facing IOS XE systems have been implanted. VulnCheck scanned internet-facing Cisco IOS XE web interfaces and found thousands of implanted hosts. This is a bad situation, as privileged access on the IOS XE likely allows attackers to monitor network traffic, pivot into protected networks, and perform any number of man-in-the-middle attacks.
Censys also configured a scan profile and published their results in a blog post. It’s not a pretty picture. Over 40K Cisco IOS devices had their web admin interfaces exposed to the internet and fell victim to the latest round of implant attacks.
More distressing is that some of these devices are being used to launch further attacks. Researchers from both VulnCheck and Censys were kind enough to run their results through the GreyNoise Analyzer, which enables bulk triage of IP lists. Over 120 devices have been put into malicious service by attackers and live in diverse autonomous systems:
Organization
Count
Akamai Technologies
23
Google APIs and Services
23
Verizon Business
11
UNINET
4
NTT Communications Corporation
3
Cogent Communications
2
Mobile Telecommunications Company
2
Reliance Jio Infocomm Limited
2
Suburban Broadband Ltd
2
UNINET-TH
2
"ElCat" Ltd.
1
aamra networks limited,
1
AMERICATEL PERU S.A.
1
Bangladesh Telecommunications Company Limited (BTCL), Nationwide PSTN Operator and Data and Internet Service Provider.
1
Bell Canada
1
Bhutan Telecom Ltd
1
CHINANET-BACKBONE
1
Cloud 9 Ltd.
1
Comcast Cable Communications, LLC
1
COMPAÑIA PARAGUAYA DE COMUNICACIONES S.A. (COPACO S.A.)
1
CRISP S.A.
1
Data Communication Business Group
1
Emirates Integrated Telecommunications Company PJSC
1
Euroweb Romania S.R.L.
1
Exetel Pty Ltd
1
Frontier Communications of America, Inc.
1
GTD PERÚ S.A
1
HBA TELECOM LTDA - ME
1
INDOSAT Internet Network Provider
1
INSYS LLC
1
IP TELECOM, SERVICOS DE TELECOMUNICACOES S.A.
1
Jamii Telecommunications Limited
1
JSC Avantel
1
JSC Comcor
1
Kenyan Post & Telecommunications Company / Telkom Kenya Ltd
1
Level 3 Parent, LLC
1
Liquid Telecommunications Ltd
1
M247 UK Ltd
1
Mobile Telecommunication Company Saudi Arabia Joint-Stock company
1
MTN COTE D'IVOIRE S.A
1
NOS COMUNICACOES, S.A.
1
Núcleo S.A.
1
Omani Qatari Telecommunication Company SAOC
1
ONE ALBANIA SH.A.
1
Philippine Long Distance Telephone Company
1
PJSC Rostelecom
1
POCOS B.V.
1
PT. Power Telecom Indonesia
1
Saudi Telecom Company JSC
1
Simbanet (T) Limited
1
SONATEL-AS Autonomous System
1
Superonline Iletisim Hizmetleri A.S.
1
Telecel S.A.
1
Telmex Colombia S.A.
1
The Communication Authoity of Thailand, CAT
1
TIEN PHAT TECHNOLOGY CORPORATION
1
Univision LLC
1
VNPT Corp
1
Vodafone Romania S.A.
1
Unsurprisingly, we’re also seeing a large uptick in scanning from malicious, benign, and “unknown” sources in our Cisco IOS XE CVE-2023-20198 Scanner tag:
Im-persistent Harms
A key aspect of the current, underlying implant is that it does not survive a reboot. That means attackers will need to reinfect devices in their control if power is cycled or if they perform regular maintenance that requires a reboot… unless they have created a persistent access method prior to the reboot such as a newly created account. Given that these Cisco appliances are (small) business-class devices, they are more likely to have static IP addresses, meaning that attackers won’t have to re-scan the entire internet nearly as often as they might otherwise to identify and re-infect them.
The Enemy Within
Censys, VulnCheck, and GreyNoise can only report the view from the outside. However, similar Cisco IOS devices are also used internally in many organizations and are equally susceptible to this vulnerability. After gaining initial access on a low-privileged endpoint, attackers will no doubt be probing for vulnerable Cisco devices internally, where it is even more likely the web admin UI will be enabled. Having such privileged access to an internal router/network may be even more valuable/desirable than internet-facing ones.
Staying Safe
Researchers from GreyNoise Labs strongly encourage organizations to disable the HTTP Server feature on all internet-facing systems until a patch is available (and consider leaving it disabled permanently). This can be done by following the instructions provided in the Cisco security advisory.
Given the transient nature of the implant, they also suggest conducting an incident response exercise to determine if any internet-facing (or internal) Cisco device was demonstrating anomalous behavior.
Remember, you can:
use our Analyzer for IP triage
block non-benign scanners — through our dynamic, timely block lists — searching for signs of implants
On October 11th, 2023, a heap-based buffer overflow in curl was disclosed under the identifier CVE-2023-38545. The vulnerability affects libcurl 7.69.0 to and including 8.3.0. Vulnerable versions of libcurl may be embedded in existing applications. However, to reach the vulnerable code path, the application must be configured to utilize one of the SOCKS5 proxy modes and attempt to resolve a hostname with extraneous length.
In a controlled environment, reproducing the bug itself is trivial. Pictured below is a vulnerable version of curl requesting a hostname consisting of 10,000 A’s through a configured SOCKS5 proxy, resulting in memory corruption leading to a Segmentation fault.
In practice, the scope of the vulnerability is more nuanced. As noted above, curl must be configured to utilize a SOCK5 proxy to reach the vulnerable code path. If you run an application utilizing a vulnerable version of curl/libcurl that makes HTTP requests and an attacker can set the “http_proxy” environment variable, curl may automatically inherit that configuration, allowing the vulnerable code path to be reached (pictured below). Of course, this assumes that the attacker already has some level of privileged access to set these environment variables. At such a point that an attacker already has privileged access, leveraging this curl vulnerability is certainly not the easiest path to remote code execution.
Through the lens of “exploit-ability” in practical deployments of curl, few could be remotely triggered. After significant research, the GreyNoise Labs team was able to identify one such configuration scenario that we would be able to track and have created a tag for detecting it. In the unlikely event that more vulnerable-in-practice applications come to light in the coming days, the tag will be updated to capture the associated traffic.
A critical zero-day vulnerability has recently been discovered in the Confluence Data Center and Server.
The vulnerability, known as CVE-2023-22515 and scored a CVSS 10 out of 10, is a privilege escalation vulnerability that allows external attackers to exploit the system and create administrator accounts that can be used to access Confluence instances.
Atlassian, the company that produces Confluence, rates this vulnerability as 'critical' and has released patches for it. On-premise instances of Confluence on the public internet are at risk as this vulnerability is exploitable anonymously. Atlassian has stated that cloud-hosted versions of Confluence are not impacted, but it is unclear if they were vulnerable before the patch. Atlassian also has published an FAQ for this vulnerability.
We recommend immediately upgrading to the latest patched version, especially if you use an exposed or internet-facing Confluence instance. Since exploitation was observed before the advisory and patch were issued, organizations should audit user accounts and signs of compromise. As a standard practice, you should also restrict network access to any Confluence instance.
GreyNoise has published a tag monitoring for CVE-2023-22515 exploitation attempts.
If you’re curious about viewing scanning activity related to the “/setup/setupadministrator.action” web path, you can view that here; and if you’re curious about IPs that are searching for any ”setup*.action” web paths, you can view that here.
(See below for the most recent update: 2023-08-03)
Citrix recently disclosed a single critical remote code execution (RCE) vulnerability, CVE-2023-3519, affecting NetScaler ADC and NetScaler Gateway (now known as Citrix ADC and Citrix Gateway. This vulnerability has a CVSS score of 9.8, making it a high-risk issue.
Over the past several days, numerous organizations have contributed their pieces of the puzzle, both publicly and privately. While the most recent Citrix Security Advisory identifies CVE-2023-3519 as the only vulnerability resulting in unauthenticated remote code execution, there are at least two vulnerabilities that were patched during the most recent version upgrade.
Through the analysis by Rapid 7 and AssetNote a memory corruption vulnerability was discovered in the ns_aaa_saml_parse_authn_request function that handles Security Assertion Markup Language (SAML), which can be reached through HTTP POST requests to “/saml/login”. This vulnerability has been demonstrated to corrupt memory and cause program crashes, but it is unknown whether it can be leveraged for remote code execution at this time.
Through the analysis by Bishop Fox’s Capabilities Development team together with GreyNoise a memory corruption vulnerability was identified in the ns_aaa_gwtest_get_event_and_target_names function. This function can be reached through HTTP GET requests to “/gwtest/formssso”. This vulnerability was demonstrated as capable of being leveraged for stack corruption, leading to remote code execution; and, was further corroborated by AssetNote’s Part 2 Analysis.
Through analysis from Mandiant some indications of compromise (IoCs) and post-exploitation activity are now known. As part of their provided IoCs they shared that an HTTP POST request was used in initial exploitation as well as HTTP payloads containing “pwd;pwd;pwd;pwd;pwd;” which may be useful for writing detection signatures.
2023-08-03 Update
On July 28th GreyNoise began observing activity — https://viz.greynoise.io/tag/citrix-adc-netscaler-cve-2023-3519-rce-attempt?days=30 — for CVE-2023-3519 wherein the attacker was attempting to leverage the vulnerability for memory corruption. An initial analysis of the observed payloads indicates that the attacker initially sends a payload containing 262 `A`'s which would result in a crash of the Citrix Netscaler `nsppe` program. They follow up with two variants using URL Encoded values and appear to be attempting to remotely execute the command `/bin/sh -c reboot` which would result in a full reboot in the system. However, it appears that the attacker may not be aware of the CPU endianness of vulnerable systems. The payloads they are attempting to send would result in memory corruption, but would not result in remote code execution as they expected. This would result in the `nsppe` program crashing.
The observed payloads are provided below for completeness.
GET /gwtest/formssso?event=start&target=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA HTTP/1.1
Host: :2375
Accept: */*
User-Agent: curl/7.29.0
GET /gwtest/formssso?event=start&target=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA%F0%C1%FF%FF%FF%7F%00%00CCCCCCCCDDDDDDDD%99Rhn%2Fshh%2F%2Fbih%20-c%20h%22rebhoot%22%89%E3QRSSj%3BX%CD%80 HTTP/1.1
Host: :2375
Accept: */*
User-Agent: curl/7.29.0
GET /gwtest/formssso?event=start&target=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA%F0%C1%FF%FF%FF%7F%00%00CCCCCCCCDDDDDDDD%99Rhn%2Fshh%2F%2Fbih%20-c%20h%22rebhoot%22%89%E3QRSSj%3BX%CD%80 HTTP/1.1
Host: :2375
Accept: */*
User-Agent: curl/7.29.0
GreyNoise observed a significant spike in attacker activity the day CISA added CVE-2023-24489 to their Known Exploited Vulnerabilities Catalog:
Citrix ShareFile, a popular cloud-based file-sharing application, has recently been found to have a critical vulnerability, CVE-2023-24489, which allows unauthenticated arbitrary file upload and remote code execution (RCE). In this blog post, we will discuss the details of this vulnerability, how attackers can exploit it, and how you can protect your organization from potential attacks.
GreyNoise now has a tag for CVE-2023-24489, allowing us to track exploit activity related to this vulnerability. If you use Citrix ShareFile, make sure to apply the latest security updates as soon as possible to patch this critical RCE flaw.
What is CVE-2023-24489?
CVE-2023-24489 is a cryptographic bug in Citrix ShareFile’s Storage Zones Controller, a .NET web application running under IIS. This vulnerability allows unauthenticated attackers to upload arbitrary files, leading to remote code execution. The vulnerability has been assigned a CVSS score of 9.8, indicating its critical severity.
How are attackers exploiting CVE-2023-24489?
Attackers can exploit this vulnerability by taking advantage of errors in ShareFile’s handling of cryptographic operations. The application uses AES encryption with CBC mode and PKCS7 padding but does not correctly validate decrypted data. This oversight allows attackers to generate valid padding and execute their attack, leading to unauthenticated arbitrary file upload and remote code execution.
Citrix has released a security update addressing the ShareFile vulnerability. Users are advised to apply the update to protect their systems from potential attacks. The fixed version of the customer-managed ShareFile storage zones controller is ShareFile storage zones controller 5.11.24 and later versions.
Leverage GreyNoise’s hourly updated data on scanning and exploit activities to stay ahead of opportunistic attackers. Our threat intelligence platform allows you to identify noise, reduce false positives, and focus on genuine threats. Sign up for GreyNoise Intelligence today and gain the edge in protecting your systems against vulnerabilities like CVE-2023-24489.
CVE-2023-29298 is an Improper Access Control vulnerability affecting Adobe ColdFusion versions 2018u16 (and earlier), 2021u6 (and earlier), and 2023.0.0.330468 (and earlier). This vulnerability could result in a security feature bypass, allowing an attacker to access the administration CFM and CFC endpoints without user interaction. The vulnerability has a CVSS 3.x base score of 7.5, indicating high severity.
CVE-2023-29300 is a Deserialization of Untrusted Data vulnerability impacting Adobe ColdFusion versions 2018u16 (and earlier), 2021u6 (and earlier), and 2023.0.0.330468 (and earlier). This vulnerability could result in arbitrary code execution without user interaction. The vulnerability has a CVSS 3.x base score of 9.8, indicating critical severity.
Citrix ADC/NetScaler Vulnerability
CVE-2023-3519 is an unauthenticated remote code execution (RCE) vulnerability impacting several versions of Citrix ADC and Citrix Gateway. This vulnerability allows a malicious actor to execute arbitrary code on affected appliances. It may also serve as an initial access vector for ransomware and other types of malicious campaigns. GreyNoise would like to thank the Capability Development team at Bishop Fox for collaborating with us to track this emerging threat. They have an excellent, detailed write-up for folks interested in more details.
CISA's Known Exploited Vulnerabilities Catalog
All three vulnerabilities are listed in CISA's Known Exploited Vulnerabilities Catalog, meaning they have been observed being exploited in the wild and pose significant risks to organizations. Organizations should prioritize remediation efforts for these vulnerabilities to reduce the likelihood of compromise by known threat actors.
Enhance Security with GreyNoise's Threat Intelligence Data
Organizations are strongly encouraged to use GreyNoise’s hourly updated threat intelligence data to block IP addresses that are seen exploiting these vulnerabilities. By leveraging GreyNoise's tags and alerts, organizations can enhance their security posture and protect their systems from potential exploitation attempts while allowing their operations teams time to apply patches or mitigations.
On June 7, 2023 VMWare released an advisory for CVE-2023-20887, a command injection vulnerability in VMware Aria Operations for Networks (formerly vRealize Cloud Mangememt) with a critical severity score (CVSS) of 9.8. The proof of concept for this exploit was released June 13th, 2023 by SinSinology.
Primary takeaway is:
“VMWare Aria Operations Networks is vulnerable to command injection when accepting user input through the Apache Thrift RPC interface. This vulnerability allows a remote unauthenticated attacker to execute arbitrary commands on the underlying operating system as the root user.” – SinSinology
At the time of writing we have observed attempted mass-scanning activity utilizing the Proof-Of-Concept code mentioned above in an attempt to launch a reverse shell which connects back to an attacker controlled server in order to receive further commands. Continual monitoring of activity related to this vulnerability can be tracked via the relevant GreyNoise tag below.
GreyNoise recommends reviewing systems for any indicators of unauthorized access that may have occurred within the past 90 days.
On May 31st, 2023 Progress issued a security notice to users of MOVEit Transfer regarding a vulnerability that allows for escalated privileges and potential unauthorized access to the environment. CVE-2023-34362 was assigned to this vulnerability on June 2, 2023. MOVEIT transfer tag can be viewed here.
Progress’ security notice is advising users to review their system for unauthorized access for “at least the past 30 days”, however, GreyNoise has observed scanning activity for the login page of MOVEit Transfer located at /human.aspx as early as March 3rd, 2023. While we have not observed activity directly related to exploitation, all of the 5 IPs we have observed attempting to discover the location of MOVEit installations were marked as “Malicious” by GreyNoise for prior activities.
Based on the scanning activity we have observed, it is our recommendation that users of MOVEit Transfer should extend the time window for their review of potentially malicious activity to at least 90 days.
The primary artifact, observed through publicly available information, is the presence of a webshell named human2.aspx. This is a post-exploitation file artifact that is written to the filesystem by a malicious actor allowing them to execute arbitrary commands.
GreyNoise is observing scanning activity looking to identify the presence of the human2.aspx webshell dropped as part of the post-exploitation activity.
While the specific details of the initial exploitation vector are largely unknown at this time, we would like to provide the following items and details to our customers and community:
Several cybersecurity vendors are covering the subject including Rapid7 and TrustedSec
Rapid7 is indicating the initial vector may be a SQL injection vulnerability leading to remote code execution (SQLi-to-RCE)
Progress MOVEit Transfer is deployed with a Microsoft SQL (MSSQL) or My SQL (MYSQL) backing database
The login page of Progress MOVEit Transfer is located at /human.aspx
Common paths to achieve remote code execution through SQL injection include the usage of the following T-SQL commands:
On Monday, May 1, 2023, CISA added CVE-2021-45046, CVE-2023-21839, and CVE-2023-1389 to the Known Exploited Vulnerabilities (KEV) list. For all three CVEs, GreyNoise users had visibility into which IPs were attempting mass exploitation prior to their addition to the KEV list. GreyNoise tags allow organizations to monitor and prioritize the handling of alerts regarding benign and, in this case, malicious IPs.
Apache Log4j2 contains a deserialization of untrusted data vulnerability due to the incomplete fix of CVE-2021-44228, where the Thread Context Lookup Pattern is vulnerable to remote code execution in certain non-default configurations.
December 9, 2021
May 1, 2023
CVE-2023-21839
Oracle WebLogic Server contains an unspecified vulnerability that allows an unauthenticated attacker with network access via T3, IIOP, to compromise Oracle WebLogic Server.
March 6, 2023
May 1, 2023
CVE-2023-1389
TP-Link Archer AX-21 contains a command injection vulnerability that allows for remote code execution.
April 25, 2023
May 1, 2023
Bonus Update:
On Thursday, April 27, 2023, GreyNoise released a tag for the critically scored CVE-2023-21554, QueueJumper, a Microsoft message queuing remote code execution vulnerability.
As of this publication, we have not observed mass exploitation attempts, but have observed >600 IPs that are attempting to discover Internet-facing Microsoft Windows devices that respond over Microsoft Message Queuing (MSMQ) binary protocol.
Check Point Research is slated to reveal full technical details later in the day on Friday, April 28, 2023.
MICROSOFT MESSAGE QUEUING (MSMQ) QUEUEJUMPER RCE ATTEMPT | CVE-2023-21554
MICROSOFT MESSAGE QUEUING (MSMQ) CRAWLER | CVES: No associated CVEs
MICROSOFT MESSAGE QUEUING (MSMQ) HTTP CRAWLER | CVES: No associated CVEs
Check Point Research discovered three vulnerabilities in Microsoft Message Queuing (MSMQ) service, patched in April's Patch Tuesday update. The most severe, QueueJumper (CVE-2023-21554), is a critical vulnerability allowing unauthenticated remote code execution. The other two vulnerabilities involve unauthenticated remote DoS attacks:
CVE-2023-21769 — unauthenticated Remote Application Level DoS (service crash)
CVE-2023-28302 — unauthenticated Remote Kernel Level DoS (Windows BSOD)
MSMQ, though considered a “legacy” service, is still available on all Windows operating systems.
According to Check Point researchers, over 360,000 IPs have the 1801/tcp port open, running the MSMQ service. The service may be enabled without user knowledge when installing certain software, such as Microsoft Exchange Server. Exploiting MSMQ vulnerabilities could allow attackers to take over servers. It's crucial for administrators to check their servers and install Microsoft's official patch. If unable to apply the patch, blocking inbound connections for 1801/tcp from untrusted sources can serve as a workaround.
GreyNoise researchers have two activity (vs exploitation attempt) tags that detect when someone is scanning to find exposed instances of the MSMQ service:
When we combine these tags, we presently see (at the time of publishing this post) just over 500 unique IP addresses — all from sources we’ve qualified as benign(👋🏼 Censys and Shadowserver!). The most prolific scanning is happening on the non-HTTP endpoint.
GreyNoise strongly recommends that organizations use our blocklists to shut down any identified malicious IPs with extreme prejudice before they have a chance to cause harm.
Our researchers are also hard at work digging into the details of each of the three weaknesses to craft specific exploitation detections which will, by default, be coming from malicious sources.
GreyNoise's detection capabilities for inventory scans of MSMQ protocols provide a reliable and essential tool in identifying and blocking malicious IPs targeting these vulnerabilities. With the accuracy of GreyNoise tags, security professionals can trust the system to highlight potential threats, allowing them to focus on other critical aspects of their organization's security. These IP Blocklists are available to all GreyNoise users now.*
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On Friday, April 21, 2023, CISA added CVE-2023-27350 (a critical unauthenticated remote code execution vulnerability) impacting PaperCut MF and PaperCut NG to the Known Exploited Vulnerabilities (KEV) list. PaperCut MF and PaperCut NG are both enterprise printer management software.
Originally ZDI-23-233, CVE-2023-27350 (CVSS 9.8) impacts both application servers and site servers for PaperCut MF and NG version 8.0 or later, according to PaperCut, and have been fixed in PaperCut MF and PaperCut NG versions 20.1.7, 21.2.11 and 22.0.9 and later.
The inclusion of this vulnerability on the KEV list implies that exploitation has been confirmed in the wild. Additionally, the PaperCut advisory also points out reports of exploitation dating back to April 13, 2023, 15:29 UTC.
GreyNoise has published two tags related to this PaperCut vulnerability:
PaperCut RCE Attempt: IP addresses with this tag have been observedattempting to exploit CVE-2023-27350, an authentication bypass vulnerability in PaperCut MF/NG that could result in remote code execution.
PaperCut Authentication Bypass Check: IP addresses with this tag have been observed checking for the existence of CVE-2023-27350, an authentication bypass vulnerability in PaperCut MF/NG.
At the time of publication, GreyNoise has not observed mass exploitation for this vulnerability but has observed two IPs mass scanning for the vulnerability; this could be for a few reasons. It could be that exploitation is happening in a more targeted fashion or simply because scanning for this vulnerability isn’t technically necessary as a specific Google search will return a few thousand hits which attackers can use to focus exploitation attempts on.
GreyNoise recommends that organizations that use PaperCut follow the vendor's guidance to upgrade and review systems for signs of compromise. (This information is included in PaperCut’s advisory).
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