CVE-2022-29638
📋 TL;DR
This CVE describes a stack overflow vulnerability in TOTOLINK A3100R routers that allows attackers to cause a Denial of Service (DoS) by sending a specially crafted POST request to the comment parameter in the setIpQosRules function. The vulnerability affects users of TOTOLINK A3100R routers running specific vulnerable firmware versions. Successful exploitation would crash the router, disrupting network connectivity.
💻 Affected Systems
- TOTOLINK A3100R
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Router becomes completely unresponsive, requiring physical power cycle to restore functionality, causing extended network downtime.
Likely Case
Router crashes and reboots automatically, causing temporary network disruption (1-3 minutes) until service is restored.
If Mitigated
No impact if router is not internet-facing or if traffic filtering blocks the exploit attempt.
🎯 Exploit Status
Exploit requires authentication to the router's web interface. The GitHub reference contains technical details that could be used to create an exploit.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available
Restart Required: No
Instructions:
No official patch available. Check TOTOLINK website for firmware updates. If update is available, download from official source, access router admin interface, navigate to firmware upgrade section, upload new firmware, and apply.
🔧 Temporary Workarounds
Disable remote administration
allPrevents external attackers from accessing the vulnerable web interface
Access router admin interface -> System Tools -> Administration -> Disable 'Remote Management'
Change default credentials
allMitigates risk by preventing unauthorized access to admin interface
Access router admin interface -> System Tools -> Administration -> Change admin password
🧯 If You Can't Patch
- Segment network to isolate router management interface
- Implement network filtering to block POST requests to vulnerable endpoint
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface: System Tools -> Firmware UpgradeCheck Version:
Not applicable - check via web interfaceVerify Fix Applied:
Verify firmware version is no longer V4.1.2cu.5050_B20200504 or V4.1.2cu.5247_B20211129📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts followed by POST requests to /cgi-bin/cstecgi.cgi with large comment parameter
- Router crash/reboot logs
Network Indicators:
- POST requests to router IP on port 80/443 with unusually large comment parameter in QoS configuration
SIEM Query:
source_ip="router_ip" AND http_method="POST" AND uri="/cgi-bin/cstecgi.cgi" AND http_user_agent CONTAINS "curl" OR "python" AND size_bytes>1000