CVE-2021-46264
📋 TL;DR
A stack buffer overflow vulnerability in Tenda AC Series Router AC11 firmware allows attackers to cause Denial of Service (DoS) by sending specially crafted data to the onlineList module. This affects users running vulnerable firmware versions on Tenda AC11 routers. The high CVSS score indicates critical severity with potential for remote exploitation.
💻 Affected Systems
- Tenda AC11 Router
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete router compromise leading to persistent DoS, potential remote code execution, and network takeover
Likely Case
Router crash requiring physical reset, temporary network disruption, and service downtime
If Mitigated
Limited to DoS impact if proper network segmentation and access controls are implemented
🎯 Exploit Status
Public GitHub repositories contain proof-of-concept code; buffer overflow exploitation is well-understood
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Later versions than AC11_V02.03.01.104_CN
Vendor Advisory: Not publicly documented by vendor
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 update 5. Reboot router
🔧 Temporary Workarounds
Network Segmentation
allIsolate router management interface from untrusted networks
Access Control Lists
allRestrict access to router management interface to trusted IPs only
🧯 If You Can't Patch
- Replace vulnerable router with updated model or different vendor
- Implement network monitoring for DoS attempts and buffer overflow patterns
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface under System Status or Firmware Update sectionCheck Version:
Not applicable - check via web interface at 192.168.0.1 or 192.168.1.1Verify Fix Applied:
Confirm firmware version is newer than AC11_V02.03.01.104_CN after update📡 Detection & Monitoring
Log Indicators:
- Router crash/reboot logs
- Unusual traffic to onlineList module
- Buffer overflow patterns in network logs
Network Indicators:
- Excessive malformed packets to router port 80/443
- DoS traffic patterns
- Unusual HTTP requests to management interface
SIEM Query:
source="router_logs" AND (event="crash" OR event="reboot") OR http_uri="/onlineList" AND content_length>normal_threshold