CVE-2021-25310
📋 TL;DR
This vulnerability allows remote authenticated attackers to execute arbitrary system commands with root privileges on Belkin Linksys WRT160NL routers. Attackers can inject shell metacharacters through the ui_language POST parameter to the apply.cgi endpoint. Only affects devices running firmware version 1.0.04.002_US_20130619 that are no longer supported.
💻 Affected Systems
- Belkin Linksys WRT160NL
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attackers to install persistent backdoors, intercept network traffic, pivot to internal networks, or brick the device.
Likely Case
Attackers with valid credentials gain full control of the router to modify configurations, steal credentials, or launch attacks against internal devices.
If Mitigated
Limited to authenticated users only, reducing exposure if strong credentials are used and network segmentation is implemented.
🎯 Exploit Status
Exploitation requires valid admin credentials. The vulnerability is well-documented with technical details publicly available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: N/A
Vendor Advisory: N/A
Restart Required: No
Instructions:
No official patch available as the product is end-of-life. Replace with supported hardware or install third-party firmware.
🔧 Temporary Workarounds
Disable Web Administration Interface
linuxDisable the vulnerable web interface to prevent exploitation
Use SSH or serial connection to disable HTTP/HTTPS services
Network Segmentation
allIsolate the router from untrusted networks
🧯 If You Can't Patch
- Replace device with supported hardware
- Install third-party firmware like OpenWRT or DD-WRT that may have security updates
🔍 How to Verify
Check if Vulnerable:
Check firmware version via web interface at http://router_ip/ or via SSH with 'cat /etc/version'Check Version:
cat /etc/versionVerify Fix Applied:
Verify web interface is disabled or device has been replaced📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /apply.cgi with shell metacharacters in ui_language parameter
- Unexpected command execution in system logs
Network Indicators:
- Suspicious traffic patterns from router to external IPs
- Unusual outbound connections from router
SIEM Query:
source="router_logs" AND uri="/apply.cgi" AND (ui_language CONTAINS "|" OR ui_language CONTAINS ";" OR ui_language CONTAINS "`")🔗 References
- https://research.nccgroup.com/2021/01/28/technical-advisory-linksys-wrt160nl-authenticated-command-injection-cve-2021-25310/
- https://research.nccgroup.com/?research=Technical%20advisories
- https://research.nccgroup.com/2021/01/28/technical-advisory-linksys-wrt160nl-authenticated-command-injection-cve-2021-25310/
- https://research.nccgroup.com/?research=Technical%20advisories
