CVE-2021-46262
📋 TL;DR
A stack buffer overflow vulnerability in the PPPoE module of Tenda AC Series Router AC11 firmware allows attackers to cause Denial of Service (DoS) by sending crafted overflow data. This affects users running the vulnerable firmware version on Tenda AC11 routers. The high CVSS score indicates critical severity with potential for remote exploitation.
💻 Affected Systems
- Tenda AC Series Router AC11
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete router crash requiring physical reset, potential remote code execution leading to full device compromise, and persistent network disruption.
Likely Case
Router becomes unresponsive requiring reboot, disrupting all network connectivity for connected devices until manually restarted.
If Mitigated
Limited to temporary service interruption if proper network segmentation and monitoring are in place.
🎯 Exploit Status
Public GitHub repositories contain proof-of-concept code. Exploitation requires network access to router's PPPoE service.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Later firmware versions (check Tenda website for latest)
Vendor Advisory: https://www.tendacn.com/en/
Restart Required: Yes
Instructions:
1. Log into router admin interface. 2. Navigate to System Tools > Firmware Upgrade. 3. Download latest firmware from Tenda website. 4. Upload and install new firmware. 5. Reboot router after installation.
🔧 Temporary Workarounds
Disable PPPoE
allIf PPPoE is not required, disable it to remove attack surface
Network Segmentation
allIsolate router management interface from untrusted networks
🧯 If You Can't Patch
- Replace router with updated model or different vendor
- Implement strict network ACLs to limit access to router management interfaces
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface under System Status or Firmware InformationCheck Version:
Login to router web interface and check System Status pageVerify Fix Applied:
Confirm firmware version is updated beyond AC11_V02.03.01.104_CN📡 Detection & Monitoring
Log Indicators:
- Router crash/reboot logs
- PPPoE service failure messages
- Unusual PPPoE connection attempts
Network Indicators:
- Sudden loss of router connectivity
- Abnormal PPPoE packet patterns
- Router becoming unresponsive to pings
SIEM Query:
source="router_logs" AND ("crash" OR "reboot" OR "PPPoE error")