CVE-2023-7095
📋 TL;DR
A critical buffer overflow vulnerability in Totolink A7100RU routers allows remote attackers to execute arbitrary code via specially crafted HTTP POST requests to the login endpoint. This affects devices running firmware version 7.4cu.2313_B20191024. Attackers can exploit this without authentication to potentially take full control of affected routers.
💻 Affected Systems
- Totolink A7100RU
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, creation of persistent backdoors, lateral movement to internal networks, and botnet recruitment.
Likely Case
Remote code execution allowing attackers to modify router configuration, intercept traffic, or use the device as a pivot point into internal networks.
If Mitigated
Limited impact if device is behind firewall with restricted HTTP access or if exploit attempts are blocked by network security controls.
🎯 Exploit Status
Public exploit code is available in GitHub repositories. The vulnerability requires sending a specially crafted HTTP POST request with buffer overflow payload.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available
Restart Required: Yes
Instructions:
1. Check Totolink website for firmware updates
2. If update available, download and verify checksum
3. Access router admin interface
4. Navigate to firmware update section
5. Upload new firmware file
6. Wait for reboot and verify version
🔧 Temporary Workarounds
Network Access Control
linuxRestrict HTTP access to router management interface
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
Disable Remote Management
allTurn off remote administration features in router settings
🧯 If You Can't Patch
- Isolate affected routers in separate network segment with strict firewall rules
- Implement network monitoring for exploit attempts and anomalous HTTP requests to /cgi-bin/cstecgi.cgi
🔍 How to Verify
Check if Vulnerable:
Check router firmware version via admin interface or by visiting http://router-ip/cgi-bin/cstecgi.cgi?action=login with monitoring for buffer overflow attemptsCheck Version:
curl -s http://router-ip/ | grep -i version or check router admin interfaceVerify Fix Applied:
Verify firmware version is no longer 7.4cu.2313_B20191024 and test with known exploit payloads (in controlled environment)📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP POST requests to /cgi-bin/cstecgi.cgi
- Large payloads in POST data
- Router crash/restart logs
Network Indicators:
- HTTP traffic to router on port 80/443 with large POST payloads
- Multiple failed login attempts followed by buffer overflow patterns
SIEM Query:
source="router_logs" AND uri="/cgi-bin/cstecgi.cgi" AND method="POST" AND (content_length>1000 OR contains(content, "flag="))