CVE-2023-31742
📋 TL;DR
This CVE describes a command injection vulnerability in Linksys WRT54GL routers that allows authenticated attackers to execute arbitrary commands with shell privileges. Attackers with web management access can inject commands through specific HTTP parameters, potentially gaining full control of affected devices. This affects Linksys WRT54GL routers running firmware version 4.30.18.006.
💻 Affected Systems
- Linksys WRT54GL
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of router with persistent backdoor installation, network traffic interception, credential theft, and lateral movement to connected devices.
Likely Case
Router takeover leading to DNS hijacking, network monitoring, and denial of service to connected devices.
If Mitigated
Limited impact if strong authentication controls and network segmentation prevent attacker access to management interface.
🎯 Exploit Status
Exploit requires authentication to web interface. Public proof-of-concept available on GitHub. Attack can be automated with simple scripts.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: None available
Vendor Advisory: http://linksys.com
Restart Required: No
Instructions:
No official patch available. Consider upgrading to supported router model or implementing workarounds.
🔧 Temporary Workarounds
Disable Remote Management
allPrevent external access to web management interface
Access router web interface > Administration > Management > Disable Remote Management
Change Default Credentials
allUse strong, unique passwords for router administration
Access router web interface > Administration > Management > Change Password
Restrict Management Access
allLimit web interface access to specific IP addresses if supported
Access router web interface > Administration > Management > Restrict Access
🧯 If You Can't Patch
- Replace router with supported model that receives security updates
- Implement network segmentation to isolate router from critical systems
🔍 How to Verify
Check if Vulnerable:
Check router firmware version via web interface: Status > Router > Firmware Version. If version is 4.30.18.006, device is vulnerable.Check Version:
Check via web interface or attempt to access http://router_ip/version.cgiVerify Fix Applied:
No official fix available. Verify workarounds by testing that remote management is disabled and strong authentication is enforced.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to router with parameters wl_ant, wl_rate, WL_atten_ctl, ttcp_num, ttcp_size containing shell metacharacters
- Multiple failed authentication attempts followed by successful login
Network Indicators:
- Unexpected outbound connections from router to external IPs
- DNS queries to suspicious domains from router
SIEM Query:
source="router_logs" AND (uri_path="/apply.cgi" OR uri_path="/start_apply.htm") AND (param="wl_ant" OR param="wl_rate" OR param="WL_atten_ctl" OR param="ttcp_num" OR param="ttcp_size") AND (value="*;*" OR value="*|*" OR value="*`*" OR value="*$(*")