Vulnerability Details CVE-2026-42376
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.002
EPSS Ranking 41.9%
CVSS Severity
CVSS v3 Score 9.8
References
Products affected by CVE-2026-42376
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cpe:2.3:h:dlink:dir-456u:a1
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cpe:2.3:o:dlink:dir-456u_firmware:-