CVE-2025-65226
📋 TL;DR
Tenda AC21 router firmware version V16.03.08.16 contains a buffer overflow vulnerability in the deviceId parameter of the /goform/saveParentControlInfo endpoint. This allows attackers to potentially execute arbitrary code or crash the device. Users running this specific firmware version on Tenda AC21 routers are affected.
💻 Affected Systems
- Tenda AC21
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, persistent backdoor installation, and lateral movement to connected networks.
Likely Case
Device crash requiring physical reset, temporary denial of service, or limited information disclosure.
If Mitigated
No impact if device is behind firewall with restricted access to management interface.
🎯 Exploit Status
Exploit requires authentication to access the vulnerable endpoint. Public proof-of-concept demonstrates buffer overflow triggering.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available
Restart Required: Yes
Instructions:
1. Check Tenda support for firmware updates. 2. Download latest firmware from official Tenda website. 3. Access router admin panel. 4. Navigate to System Tools > Firmware Upgrade. 5. Upload new firmware file. 6. Wait for automatic reboot.
🔧 Temporary Workarounds
Disable remote management
allPrevent external access to router web interface
Access router admin panel > System Tools > Remote Management > Disable
Disable parental control feature
allRemove access to vulnerable endpoint
Access router admin panel > Parental Control > Disable
🧯 If You Can't Patch
- Isolate router on separate VLAN with restricted access
- Implement network firewall rules to block access to port 80/443 on router from untrusted networks
🔍 How to Verify
Check if Vulnerable:
Access router web interface, check firmware version in System Status or About pageCheck Version:
curl -s http://router-ip/goform/getStatus | grep versionVerify Fix Applied:
Verify firmware version is different from V16.03.08.16📡 Detection & Monitoring
Log Indicators:
- Repeated POST requests to /goform/saveParentControlInfo with long deviceId parameters
- Router crash/reboot logs
Network Indicators:
- Unusual HTTP traffic to router management interface with oversized POST parameters
SIEM Query:
source="router.log" AND (url="/goform/saveParentControlInfo" AND content_length>1000)