Unrated

Authenticated command injection in Prolink PRC2402M applogin.cgi

IdentifiersCVE-2021-35404CWE-78

CVE-2021-35404 is an authenticated OS command injection vulnerability in the Prolink PRC2402M router, observed on firmware version 20190909. The flaw is in the /cgi-bin/applogin.cgi CGI handler. When the api parameter is set to app, applogin.cgi invokes sys_login1, which retrieves user-controlled parameters including ipaddr, password, and lang. After validating the supplied password against the expected MD5 value, the code constructs a shell command using sprintf and executes it via do_system, a wrapper around system. Because the ipaddr and lang parameters are incorporated into the shell command without proper validation or sanitization, an authenticated attacker can inject shell metacharacters and execute arbitrary commands. The injected commands run in the context of the root user.

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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 yields arbitrary command execution as root on the affected router. This gives an attacker full control of the device, including the ability to modify configuration, access or alter sensitive data, install persistent payloads, pivot within the local network, and disrupt router operation.

Mitigation

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

Until patched firmware is deployed, restrict access to the router administrative interface and CGI endpoints such as /cgi-bin/applogin.cgi to trusted management networks only. Disable WAN-side administrative exposure if enabled. Limit authenticated access to trusted administrators, rotate administrative credentials, and monitor for suspicious requests containing shell metacharacters in parameters such as lang or ipaddr.

Remediation

Patch, then assume compromise.

Apply the vendor-provided fix from Prolink. The disclosure timeline in the provided content indicates the issue was fixed by the vendor on 2021-06-13. If a patched firmware release is available for the PRC2402M, upgrade to that version or later.

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-20221-35404) Prolink PRC2402M applogin.cgi sys_login1 Authenticated Command Injection Vulnerability | STAR Labs

An authenticated command injection vulnerability in the Prolink PRC2402M router's applogin.cgi endpoint that allows arbitrary code execution as root due to unsanitized user input being passed to system.

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Exposure mapping

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Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

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

Social activity