The Fallback Password: Dissecting the Tenda Router Backdoor (CVE-2026-11405)
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Tenda router backdoor analysis, deep security vulnerability dissection relevant to infrastructure.
CVE-2026-11405 reveals an authentication bypass in Tenda router firmware where the login() function in /bin/httpd falls back to a runtime-read config key (sys.rzadmin.password) via GetValue() after primary MD5-hashed credential check fails, granting admin access without username validation. CERT/CC disclosed the vulnerability on July 6, 2026, after Tenda failed to respond to a May 19 notification, and no patch is available for affected models including FH1201, W15E, AC10, AC5, and AC6. Unlike hardcoded backdoors, this architecturally sneakier mechanism stores the fallback password per-device in NVRAM, evading static binary analysis and suggesting an engineering support mechanism shipped to production.