CVE-2026-42376
published 2026-05-04CVE-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…
PriorityP267critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EPSS
0.46%
36.6th percentile
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.
Affected
1 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| d-link | dir-456u_firmware | — | — |
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VulDB
D-Link DIR-456U A1 S80telnetd.sh strcmp hard-coded credentials
vuldb·2026-05-04·CVSS 9.8
CVE-2026-42376 [CRITICAL] D-Link DIR-456U A1 S80telnetd.sh strcmp hard-coded credentials
A vulnerability classified as critical was found in D-Link DIR-456U A1. This vulnerability affects the function strcmp of the file /etc/init0.d/S80telnetd.sh. The manipulation results in hard-coded credentials. This vulnerability only affects products that are no longer supported by the maintainer.
This vulnerability is known as CVE-2026-42376. Access to the local network is required for this attack. No exploit is available.
GHSA
GHSA-8fmw-7p6g-ww4q: D-Link DIR-456U Hardware Revision A1 (End-of-Life, EOL) contains a hardcoded telnet backdoor
ghsa_unreviewed·2026-05-04
CVE-2026-42376 [CRITICAL] CWE-798 GHSA-8fmw-7p6g-ww4q: D-Link DIR-456U Hardware Revision A1 (End-of-Life, EOL) contains a hardcoded telnet backdoor
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.
No detection rules found.
No public exploits indexed.
No writeups or analysis indexed.
2026-05-04
Published