A remote code execution vulnerability in D-Link NAS devices is actively being exploited and is tracked under CVE-2024-3273. The vulnerability is believed to affect as many as 92,000 devices and further information can be found on D-Link’s support announcement.

(04/11/2024): Clarification on CVE-2024-3273 & CVE-2024-3272

Exploitation of the CVE-2024-3273 command injection vulnerability requires the two valid `user=` and `passwd=` parameters. There is a companion vulnerability tracked as CVE-2024-3272 and describes the issue as "manipulation of the argument user with the input messagebus leads to hard-coded credentials". It is important to note that the "credentials" as described are only the username for the user "messagebus".

"messagebus" is not a backdoor account. It is one of many common pre-configured linux system users that functionally cannot "log in", and thus have no password. Other common example system users include avahi, syslog, nobody, ntp, rtkit, and whoopsie. D-Link correctly validates that the username exists and also correctly validates that the provided password is correct. The logic flaw exercised by CVE-2024-3273 is that the empty (correct) password for the "messagebus" user is never validated that the user should ever be able to log in using a password, if at all.

(04/09/2024): Update on number of vulnerable devices

Upon further analysis, it appears the number of vulnerable devices is much lower than initially reported.  According to our friends at Censys, the number is closer to 5,500 devices.

GreyNoise quickly released a tag for tracking under D-Link NAS CVE-2024-3273 RCE Attempt, which was relatively easy for us because our Sift tooling surfaced the exploit to us automatically. Sift curates a report of new/interesting traffic observed by GreyNoise sensors daily after doing much of the analysis and triage work itself.

You can read more about Sift and check it out for yourself at https://sift.labs.greynoise.io/

Sift’s analysis above is correct! Taking it a step further, the command the above IP is attempting to execute is a generic shell script pattern used by botnet operators to try to execute malware for every possible CPU architecture in the expectation that at least one will work. The malware is fetched from 38[.]6[.]224[.]248 over HTTP.

We have retrieved the sample skid.x86 and uploaded it to VirusTotal for sharing and further analysis:

This article is a summary of the full, in-depth version on the GreyNoise Labs blog.
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