Unpatched Backdoor in Tenda Firmware Grants Admin Access to Devices
A critical undocumented backdoor (CVE-2026-11405) in Tenda firmware allows authentication bypass by validating a hardcoded plaintext password against any username, granting full administrative access. The vulnerability stems from flawed logic in the web server's login function, where failed authentications trigger a fallback check against a static configuration value without verifying the associated user identity. CERT/CC reported an inability to coordinate with the vendor, resulting in no avail
Analysis
TL;DR
- A critical undocumented backdoor (CVE-2026-11405) in Tenda firmware allows authentication bypass by validating a hardcoded plaintext password against any username, granting full administrative access.
- The vulnerability stems from flawed logic in the web server's login function, where failed authentications trigger a fallback check against a static configuration value without verifying the associated user identity.
- CERT/CC reported an inability to coordinate with the vendor, resulting in no available patches and forcing reliance on mitigation strategies such as disabling remote management.
- A separate unpatched vulnerability (CVE-2026-13753) in HP Deskjet printers exposes sensitive configuration data via unauthenticated API endpoints due to missing authorization checks.
Why It Matters
This incident highlights severe lapses in secure coding practices within consumer IoT and networking hardware, specifically regarding hardcoded credentials and improper authentication flows. For security practitioners, it underscores the critical importance of supply chain security and the risks associated with vendors failing to respond to responsible disclosure efforts.
Technical Details
- Vulnerability Mechanism: In Tenda devices, when standard authentication fails, the system retrieves a password from the configuration file and compares it in plaintext with the user-supplied input. If they match, access is granted regardless of the username provided.
- Impact Scope: The flaw affects multiple Tenda routers, switches, and networking devices, allowing attackers to modify network settings, disable security features, and compromise the local network.
- HP Printer Flaw: CVE-2026-13753 involves HP Deskjet 2800 series printers where GET requests to backend API endpoints bypass authentication and session validation, leaking Wi-Fi passphrases and serial numbers.
- Remediation Status: No patches have been released for either vulnerability. CERT/CC recommends disabling remote web management and changing default LAN IPs to mitigate exposure.
Industry Insight
- Vendor Accountability: The failure of CERT/CC to coordinate with Tenda suggests a broader issue in the IoT sector where vendors may lack robust security response teams, necessitating stricter regulatory oversight or mandatory security standards.
- Defense in Depth: Organizations and consumers must assume default configurations are insecure; proactive measures like network segmentation and disabling unused services (e.g., remote management) are essential defenses against unpatched vulnerabilities.
- API Security Audits: The HP printer case reinforces the need for rigorous authorization checks on all API endpoints, particularly those handling sensitive configuration data, to prevent information leakage even in non-administrative contexts.
Disclaimer: The above content is generated by AI and is for reference only.