Vulnerability · Published Jul 6, 2026 · Assigned by certcc
CVE-2026-11405Hidden backdoor authentication mechanism in multiple versions of Tenda firmware allows admin access to web management interface
Critical 9.8
In plain English
A critical-severity security flaw in firmware from Tenda. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 56% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.
Official description
The web server binary /bin/httpd contains a hidden backdoor authentication mechanism in the login() function at 004c88b8. - The function contains a normal authentication path using MD5/hash-based password verification (prod_encode64/PasswordToMd5/check_rand_key). - After normal authentication fails, it calls GetValue("sys.rzadmin.password") to read a backdoor password from the device configuration. - It performs a direct strcmp() comparison (plaintext, not hashed) between the config value and the user-supplied password. A successful match grants role=2 (admin-level access) and creates a valid session. The rzadmin username is never checked — any username works with the backdoor