CVE-2025-15255
📋 TL;DR
A remote stack-based buffer overflow vulnerability in Tenda W6-S routers allows attackers to execute arbitrary code by manipulating Cookie parameters in HTTP requests. This affects Tenda W6-S routers running firmware version 1.0.0.4(510). Attackers can exploit this without authentication to potentially take full control of affected devices.
💻 Affected Systems
- Tenda W6-S
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise leading to persistent backdoor installation, network traffic interception, lateral movement to internal networks, and botnet recruitment.
Likely Case
Remote code execution allowing attackers to modify router settings, intercept traffic, or use the device as a pivot point for further attacks.
If Mitigated
Limited impact if devices are behind firewalls with strict inbound filtering and network segmentation prevents lateral movement.
🎯 Exploit Status
Public exploit code is available in GitHub repositories. The vulnerability requires sending a specially crafted HTTP request with manipulated Cookie header to trigger the buffer overflow.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: https://www.tenda.com.cn/
Restart Required: Yes
Instructions:
1. Check Tenda website for firmware updates. 2. Download latest firmware for W6-S. 3. Access router admin interface. 4. Navigate to System Tools > Firmware Upgrade. 5. Upload and install new firmware. 6. Reboot router after installation.
🔧 Temporary Workarounds
Block External Access to Router Admin
allConfigure firewall to block inbound connections to router web interface (port 80/443) from external networks.
Disable Remote Management
allTurn off remote management feature in router settings to prevent external access to admin interface.
🧯 If You Can't Patch
- Isolate affected routers in separate VLAN with strict firewall rules limiting communication to management network only.
- Implement network-based intrusion prevention systems (IPS) to detect and block exploitation attempts targeting this vulnerability.
🔍 How to Verify
Check if Vulnerable:
Check router firmware version via admin interface at System Status > Firmware Version. If version is exactly 1.0.0.4(510), device is vulnerable.Check Version:
curl -s http://router-ip/ | grep -i firmware || ssh admin@router-ip 'cat /proc/version'Verify Fix Applied:
After firmware update, verify version has changed from 1.0.0.4(510) to a newer version. Test with controlled exploitation attempt to confirm fix.📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP requests with malformed Cookie headers to /bin/httpd
- Multiple failed authentication attempts followed by buffer overflow patterns
- Router process crashes or unexpected reboots
Network Indicators:
- HTTP requests with unusually long Cookie headers (>1000 characters)
- Traffic patterns showing exploitation attempts from external IPs
- Unexpected outbound connections from router to suspicious destinations
SIEM Query:
source="router_logs" AND (http_cookie_length>1000 OR http_uri="/bin/httpd")