CVE-2025-13446
📋 TL;DR
This vulnerability in Tenda AC21 routers allows remote attackers to execute arbitrary code via a stack-based buffer overflow in the SetSysTimeCfg endpoint. Attackers can exploit this without authentication to potentially take full control of affected devices. All users of Tenda AC21 routers with firmware version 16.03.08.16 are affected.
💻 Affected Systems
- Tenda AC21
📦 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 device settings, intercept traffic, or use the device as a pivot point into internal networks.
If Mitigated
Limited impact if devices are behind firewalls with strict inbound filtering and network segmentation prevents lateral movement.
🎯 Exploit Status
Exploit code is publicly available on GitHub, making exploitation trivial for attackers with basic skills.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: None available
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
Network Access Control
linuxBlock external access to router web interface
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
Endpoint Disable
allDisable vulnerable endpoint if possible via configuration
🧯 If You Can't Patch
- Isolate affected routers in separate VLAN with strict firewall rules
- Implement network monitoring for exploitation attempts and block malicious IPs
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface under System Status or About pageCheck Version:
curl -s http://router-ip/goform/getStatus | grep versionVerify Fix Applied:
Verify firmware version is no longer 16.03.08.16 after update📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /goform/SetSysTimeCfg
- Multiple failed buffer overflow attempts in system logs
- Unexpected process execution or system reboots
Network Indicators:
- HTTP POST requests to /goform/SetSysTimeCfg with long timeZone parameters
- Traffic from router to suspicious external IPs
SIEM Query:
source="router_logs" AND (uri="/goform/SetSysTimeCfg" OR "buffer overflow" OR "segmentation fault")🔗 References
- https://github.com/Madgeaaaaa/MY_VULN_2/blob/main/Tenda/VULN8.md
- https://github.com/Madgeaaaaa/MY_VULN_2/blob/main/Tenda/VULN9.md
- https://vuldb.com/?ctiid.333018
- https://vuldb.com/?id.333018
- https://vuldb.com/?submit.694425
- https://vuldb.com/?submit.694430
- https://www.tenda.com.cn/
- https://github.com/Madgeaaaaa/MY_VULN_2/blob/main/Tenda/VULN8.md
- https://github.com/Madgeaaaaa/MY_VULN_2/blob/main/Tenda/VULN9.md
