CVE-2026-42376
CriticalSummary
D-Link DIR-456U Hardware Revision A1 contains a hardcoded telnet backdoor. The device starts a telnet daemon at boot, allowing access to a root shell with full administrative control.
Risk Assessment
An attacker on the local network can gain full access to the device, posing a serious security threat. Additionally, the device has reached End-of-Life (EOL) and will not receive patches.
Recommendation
It is recommended to immediately disable the device or replace it with a model that does not have known vulnerabilities. Access to the device from the local network should also be blocked.
Original NVD description (English source)
D-Link DIR-456U Hardware Revision A1 (End-of-Life, EOL) contains a hardcoded telnet backdoor. The device starts a telnet daemon at boot via /etc/init0.d/S80telnetd.sh with the username "Alphanetworks" and the static password "whdrv01_dlob_dir456U" read from /etc/config/image_sign. The custom telnetd binary accepts a -u user:password flag, and the custom login binary uses strcmp() to validate credentials. Successful authentication grants an unauthenticated attacker on the local network a root shell with full administrative control. The device has reached End-of-Life (EOL) and will not receive patches.