CVE-2025-8131
📋 TL;DR
This critical vulnerability in Tenda AC20 routers allows remote attackers to execute arbitrary code via a stack-based buffer overflow in the SetStaticRouteCfg functionality. Attackers can exploit this without authentication to potentially take full control of affected routers. All users of Tenda AC20 routers with the vulnerable firmware are affected.
💻 Affected Systems
- Tenda AC20
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of router with persistent backdoor installation, credential theft, network traffic interception, and pivot to internal network devices.
Likely Case
Router takeover leading to DNS hijacking, credential harvesting, and botnet recruitment for DDoS attacks.
If Mitigated
Limited impact if router is behind firewall with restricted WAN access, though internal network exposure remains.
🎯 Exploit Status
Public exploit code exists on GitHub, making this easily weaponizable. The buffer overflow manipulation is straightforward for attackers with basic skills.
🛠️ 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. 3. Access router admin interface. 4. Navigate to firmware upgrade section. 5. Upload and apply new firmware. 6. Reboot router.
🔧 Temporary Workarounds
Disable WAN Management
allPrevent remote exploitation by disabling router management from WAN/Internet interface
Network Segmentation
allIsolate router management interface to separate VLAN with strict access controls
🧯 If You Can't Patch
- Replace affected Tenda AC20 routers with different models or brands
- Place router behind dedicated firewall with strict ingress filtering and IDS/IPS rules
🔍 How to Verify
Check if Vulnerable:
Access router web interface, navigate to System Status or About page, check firmware version matches 16.03.08.05Check Version:
curl -s http://router-ip/goform/getStatus | grep versionVerify Fix Applied:
After firmware update, verify version is different from 16.03.08.05 and test SetStaticRouteCfg endpoint is no longer accessible or properly validates input📡 Detection & Monitoring
Log Indicators:
- Multiple POST requests to /goform/SetStaticRouteCfg with long parameter values
- Router crash/reboot logs
- Unusual outbound connections from router
Network Indicators:
- Exploit traffic patterns matching public PoC
- Unusual traffic from router to external IPs
- DNS queries to suspicious domains from router
SIEM Query:
source="router_logs" AND (uri="/goform/SetStaticRouteCfg" OR "buffer overflow" OR "segmentation fault")🔗 References
- https://github.com/Thir0th/Thir0th-CVE/blob/main/Tenda_AC20_V16.03.08.05_has_a_stack_overflow.md
- https://vuldb.com/?ctiid.317527
- https://vuldb.com/?id.317527
- https://vuldb.com/?submit.619769
- https://www.tenda.com.cn/
- https://github.com/Thir0th/Thir0th-CVE/blob/main/Tenda_AC20_V16.03.08.05_has_a_stack_overflow.md
