Unrated

Unauthenticated Command Injection in PROLiNK PRC2402M touchlist_sync.cgi

IdentifiersCVE-2021-35403CWE-78

CVE-2021-35403 is an unauthenticated OS command injection vulnerability in the PROLiNK PRC2402M router, observed on firmware version 20190909. The flaw is in the CGI handler /cgi-bin/touchlist_sync.cgi, where attacker-controlled input from the IP query parameter is incorporated into a shell command that is executed via popen without proper validation or sanitization. The vulnerable code constructs a command of the form "curl -s -m 5 http://%s/cgi-bin/touchlist_sync.cgi?getACL=1" using the supplied IP value and then executes it with popen. Because the IP parameter is not safely constrained, an attacker can inject shell metacharacters and arbitrary commands. The vulnerable path is reachable when getACL is not equal to "1" and the device NVRAM MeshMode value is set to "1" or "2".

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows arbitrary command execution as root on the affected router. Because the issue is unauthenticated and reachable over HTTP, it can permit full compromise of the device, including modification of configuration, execution of follow-on payloads, persistence, interception or manipulation of network traffic, and use of the router as a pivot point within the local network.

Mitigation

If you can’t patch tonight, do this now.

If patching is not immediately possible, restrict access to the router’s web/CGI management interface from untrusted networks, especially WAN exposure. Disable remote administration where feasible, segment management access to trusted hosts only, and use firewall rules or ACLs to block external access to /cgi-bin/touchlist_sync.cgi. Monitoring for crafted requests to that endpoint containing shell metacharacters in the IP parameter may help detect exploitation attempts. These are temporary mitigations and do not remove the underlying flaw.

Remediation

Patch, then assume compromise.

Apply the vendor-issued fix from PROLiNK for CVE-2021-35403. The vendor reportedly acknowledged the issue on 2021-06-10, accepted a bypass to an initial patch on 2021-06-11, and issued a final fix on 2021-06-13. Remediation should ensure that user-controlled input is never concatenated into shell commands, replacing shell-based invocation patterns with safe APIs and strict allowlist validation for the IP parameter.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

ACTIVITY FEED

Recent activity

2 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

2 SOURCESView more in app

starlabs sgNews

Aug 4, 2021

Identifying Bugs in Router Firmware at Scale with Taint Analysis | STAR Labs

A command injection vulnerability affecting the PROLiNK PRC2402M router.

starlabs sgNews

Jun 10, 2021

(CVE-20221-35403) Prolink PRC2402M touchlist_sync.cgi main Un-authenticated Command Injection Vulnerability | STAR Labs

An unauthenticated command injection vulnerability in the Prolink PRC2402M router's touchlist_sync.cgi endpoint that allows arbitrary code execution as root.

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Exposure mapping

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Threat actor evidence

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Associated malware

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Detection signatures

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Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity