CVE-2026-42376
D-Link DIR-456U A1 Hardcoded Telnet Backdoor Credentials
- State
- Published
- Severity
- 9.8 Critical
- Published
- May 4, 2026
- Updated
- May 4, 2026
- Reserved
- Apr 27, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 9.8 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H | securin |
Weaknesses
- CWE-798 Use of Hard-coded Credentials
Affected Products
| Product | Versions |
|---|---|
DIR-456U FirmwareD-Link |
|
References
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