Quick Takeaways
- Attackers can exploit a hidden backdoor in Tenda firmware (CVBE-2026-11405) to gain full administrative access without valid credentials.
- The backdoor bypasses normal password verification by directly comparing a secret configuration password with user input, enabling remote device control.
- Successful exploitation can allow unauthorized configuration changes, security disablement, and potential full takeover of affected devices.
Threat, Attack Techniques, and Targets
CERT/CC warned about a hidden admin backdoor in Tenda router firmware. Several firmware versions are affected. An attacker can use this backdoor to control the web management interface. The backdoor is inside the “login()” function in the “/bin/httpd” server. It works by bypassing normal password checks. The attacker fetches a special password from the device configuration and compares it with what the user enters. If they match, full admin access is granted. This method does not check the username, so any username will work with the backdoor password. The attack targets Tenda routers susceptible to this vulnerability. It can be exploited remotely and silently.
Impact, Security Implications, and Remediation Guidance
The vulnerability allows attackers to take full control of the router’s web interface. They can change settings, disable security features, or reconfigure the device. This could lead to complete device takeover and potentially compromise the entire network. Because the backdoor is undocumented, it is difficult for users to detect or defend against. The vulnerability remains unpatched at this time. Users should contact Tenda or relevant authorities for remediation guidance. Meanwhile, it is advised to disable remote management and change the default LAN IP address. These steps can help reduce the risk of exploitation and limit attacker access.
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