CVE-2026-2871
📋 TL;DR
CVE-2026-2871 is a remote stack-based buffer overflow vulnerability in Tenda A21 routers. Attackers can exploit this to execute arbitrary code or crash the device by sending specially crafted requests to the /goform/SetIpMacBind endpoint. This affects all users of Tenda A21 routers running version 1.0.0.0.
💻 Affected Systems
- Tenda A21
📦 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
Remote denial of service (device crash) or limited code execution to modify router settings.
If Mitigated
Attack attempts cause crashes but no persistent compromise if proper network segmentation exists.
🎯 Exploit Status
Public exploit code is available on GitHub. The vulnerability requires no authentication and has straightforward exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: None available
Restart Required: Yes
Instructions:
1. Check Tenda's official website for firmware updates. 2. If an update exists, download the firmware file. 3. Log into router web interface. 4. Navigate to System Tools > Firmware Upgrade. 5. Upload and install the new firmware. 6. Wait for router to reboot.
🔧 Temporary Workarounds
Disable Remote Management
allPrevent external access to router web interface
Network Segmentation
allIsolate router management interface to trusted network segment
🧯 If You Can't Patch
- Replace affected routers with different models or brands
- Implement strict firewall rules blocking all access to port 80/443 on router IP except from trusted management stations
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in web interface: System Status > Firmware Version. If version is 1.0.0.0, device is vulnerable.Check Version:
curl -s http://router-ip/ | grep -i firmware || wget -qO- http://router-ip/Verify Fix Applied:
After firmware update, verify version is no longer 1.0.0.0. Test by attempting to access /goform/SetIpMacBind with malformed data (in controlled environment).📡 Detection & Monitoring
Log Indicators:
- Multiple POST requests to /goform/SetIpMacBind with unusually long parameters
- Router crash/reboot logs
- Memory corruption errors in system logs
Network Indicators:
- HTTP POST requests to /goform/SetIpMacBind with oversized parameter values
- Sudden loss of connectivity to router management interface
SIEM Query:
source="router_logs" AND (url="/goform/SetIpMacBind" AND content_length>1000) OR event="buffer overflow" OR event="segmentation fault"