CVE-2026-42376: D-Link DIR-456U A1 Hardcoded Telnet Backdoor Credentials
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 "whdrv01dlobdir456U" read from /etc/config/imagesign. 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.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-42376?
CVE-2026-42376 is considered a critical vulnerability due to the presence of hardcoded telnet backdoor credentials.
How do I fix CVE-2026-42376?
To mitigate CVE-2026-42376, disconnect the D-Link DIR-456U A1 from the network and consider replacing it, as it is beyond end-of-life support.
What are the default credentials for CVE-2026-42376?
The default credentials for CVE-2026-42376 are the username "Alphanetworks" and the static password "whdrv01_dlob_dir4."
What devices are affected by CVE-2026-42376?
CVE-2026-42376 affects the D-Link DIR-456U hardware revision A1.
Is CVE-2026-42376 related to remote access vulnerabilities?
Yes, CVE-2026-42376 is related to remote access vulnerabilities due to the hardcoded telnet backdoor allowing unauthorized access.