CVE-2020-22079
📋 TL;DR
This is a critical stack-based buffer overflow vulnerability in Tenda AC-10U routers that allows remote attackers to execute arbitrary code by sending a specially crafted timeZone parameter. Attackers can gain full control of affected routers without authentication. All users of vulnerable Tenda AC-10U router versions are affected.
💻 Affected Systems
- Tenda AC-10U AC1200 Router
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete router compromise allowing attackers to intercept all network traffic, install persistent malware, pivot to internal networks, and use the router as part of a botnet.
Likely Case
Router takeover enabling traffic interception, DNS hijacking, credential theft, and lateral movement into connected devices.
If Mitigated
Limited impact if routers are behind firewalls with strict inbound filtering, though internal attacks remain possible.
🎯 Exploit Status
Multiple public PoCs exist demonstrating remote code execution. The vulnerability requires no authentication and has simple exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Tenda for firmware updates beyond V15.03.06.48
Vendor Advisory: Not specified in provided references
Restart Required: Yes
Instructions:
1. Log into router admin interface. 2. Navigate to firmware update section. 3. Download latest firmware from Tenda website. 4. Upload and apply firmware update. 5. Reboot router.
🔧 Temporary Workarounds
Disable Remote Management
allPrevent external access to router web interface
Network Segmentation
allIsolate router management interface to trusted network
🧯 If You Can't Patch
- Replace affected routers with patched or different models
- Implement strict firewall rules blocking all inbound access to router management interface
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface. If version is V15.03.06.48 or earlier, assume vulnerable.Check Version:
Check via router web interface or SSH if enabled: cat /proc/version or show version commandsVerify Fix Applied:
Confirm firmware version has been updated to a version later than V15.03.06.48📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to goform/SetSysTimeCfg with long timeZone parameters
- Failed authentication attempts followed by exploitation attempts
Network Indicators:
- HTTP POST requests to router IP on port 80 with abnormal timeZone parameter length
- Sudden outbound connections from router to suspicious IPs
SIEM Query:
source_ip=router_ip AND http_method=POST AND uri_path="*goform/SetSysTimeCfg*" AND content_length>100🔗 References
- https://cwe.mitre.org/data/definitions/121.html
- https://github.com/1sd3d/Tendown/tree/master/PoCs/Auth/bof11
- https://github.com/Lyc-heng/routers/blob/main/routers/stack1.md
- https://cwe.mitre.org/data/definitions/121.html
- https://github.com/1sd3d/Tendown/tree/master/PoCs/Auth/bof11
- https://github.com/Lyc-heng/routers/blob/main/routers/stack1.md
