CVE-2026-1638
📋 TL;DR
This CVE describes a remote command injection vulnerability in Tenda AC21 routers. Attackers can execute arbitrary commands on affected devices by manipulating the dmzIp parameter in the mDMZSetCfg function. All users of vulnerable Tenda AC21 routers with internet-facing administration interfaces are at risk.
💻 Affected Systems
- Tenda AC21
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attackers to install persistent backdoors, intercept network traffic, pivot to internal networks, or use the device for botnet activities.
Likely Case
Remote code execution leading to device takeover, credential theft, DNS hijacking, or participation in DDoS attacks.
If Mitigated
Limited impact if device is behind firewall with restricted WAN access and strong authentication.
🎯 Exploit Status
Public exploit code is available on GitHub. The vulnerability requires no authentication and has simple exploitation vectors.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: https://www.tenda.com.cn/
Restart Required: No
Instructions:
1. Check Tenda website for firmware updates. 2. Download latest firmware. 3. Log into router admin interface. 4. Navigate to firmware upgrade section. 5. Upload and apply new firmware.
🔧 Temporary Workarounds
Disable WAN Administration
allPrevent remote access to router administration interface from internet
Network Segmentation
allPlace router in isolated network segment with restricted access
🧯 If You Can't Patch
- Disable DMZ functionality completely in router settings
- Implement strict firewall rules to block all WAN access to router administration ports
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface. If version is 16.03.08.16, device is vulnerable.Check Version:
Login to router admin interface and check System Status or Firmware Version pageVerify Fix Applied:
After firmware update, verify version has changed from 16.03.08.16 and test if /goform/mDMZSetCfg endpoint still accepts malicious input.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /goform/mDMZSetCfg
- Suspicious command execution in router logs
- Multiple failed authentication attempts
Network Indicators:
- Unusual outbound connections from router
- Traffic to known malicious IPs
- Port scanning originating from router
SIEM Query:
source="router_logs" AND (uri="/goform/mDMZSetCfg" OR command="*;*" OR command="*|*")