Full Report
Several versions of firmware released by Chinese network device manufacturer Tenda have been found to embed an undocumented authentication backdoor that enables administrative access to the devices’ web management interfaces, the CERT Coordination Center (CERT/CC) warned Monday. “An attacker can exploit this vulnerability, tracked as CVE-2026-11405, to bypass the password verification process and obtain full administrative…
Analysis Summary
# Vulnerability: Undocumented Administrative Backdoor in Tenda Router Firmware
## CVE Details
- **CVE ID:** CVE-2026-11405
- **CVSS Score:** Not explicitly listed (Estimated: Critical)
- **CWE:** CWE-259: Use of Hardcoded Password / CWE-798: Use of Hardcoded Credentials (implied by "undocumented authentication backdoor")
## Affected Systems
- **Products:** Various network devices manufactured by Tenda.
- **Versions:** Multiple firmware versions (specific model lists often maintained by CERT/CC).
- **Configurations:** Devices running the web management interface via the `/bin/httpd` binary.
## Vulnerability Description
An undocumented authentication backdoor exists within the `login()` function of the `/bin/httpd` web server binary. The firmware typically utilizes MD5-based password verification for standard logins; however, researchers discovered an alternate code path. If the standard authentication process fails, this secondary path can be triggered to grant full administrative access, effectively bypassing the legitimate password verification process.
## Exploitation
- **Status:** Vulnerability publicly disclosed; high risk of exploitation following CERT/CC alert.
- **Complexity:** Low (Bypasses standard credential requirements).
- **Attack Vector:** Network (Access to the web management interface).
## Impact
- **Confidentiality:** High (Full access to device configuration and traffic logs).
- **Integrity:** High (Ability to modify settings, DNS, or firmware).
- **Availability:** High (Ability to disable the device or disrupt network services).
## Remediation
### Patches
- Users are advised to check the official Tenda support website for firmware updates corresponding to their specific model.
### Workarounds
- **Disable Remote Management:** Ensure the web management interface is not accessible from the Wide Area Network (Internet).
- **Restrict Local Access:** Use VLANs or physical security to limit which local devices can reach the router's login page.
- **Replace Legacy Hardware:** If a specific model is end-of-life and not receiving updates, consider replacing it with a supported device.
## Detection
- **Indicators of Compromise:** Monitor for unauthorized configuration changes or administrative logins occurring from unexpected IP addresses.
- **Detection Methods and Tools:** Network scanners may identify the exposure of the `httpd` service. Security teams can analyze firmware binaries for the specific logic branch in the `login()` function.
## References
- **Vendor Advisories:** hxxps[://]www[.]tendacn[.]com/support/default[.]html
- **Relevant Links:**
- hxxps[://]kb[.]cert[.]org/vuls/id/213560
- hxxps[://]www[.]cve[.]org/CVERecord?id=CVE-2026-11405
- hxxps[://]thehackernews[.]com/2026/07/certcc-warns-of-hidden-admin-backdoor[.]html