CVE-2026-42375

D-Link DIR-600L A1 Hardcoded Telnet Backdoor Credentials

Published May 4, 2026 CVSS 3.1 · 9.8 Critical EPSS < 1% KEV · Not listed
Description
D-Link DIR-600L Hardware Revision A1 (End-of-Life) contains a hardcoded telnet backdoor. The device starts a telnet daemon at boot via /bin/telnetd.sh with the username "Alphanetworks" and the static password "wrgn35_dlwbr_dir600l" read from /etc/alpha_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.

Remediation

Vendor Workaround

This product is End-of-Life and will NOT receive patches. Users should replace the device. Temporary: connect via backdoor and run "killall telnetd" and "iptables -A INPUT -p tcp --dport 23 -j DROP" (lost on reboot).

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Dlink dir-600l
CPEs cpe:2.3:h:dlink:dir-600l:a1:*:*:*:*:*:*:*
Vendors & Products Dlink dir-600l
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'total'}, 'version': '2.0.3'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared D-link
D-link dir-600l Firmware
Vendors & Products D-link
D-link dir-600l Firmware
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description D-Link DIR-600L Hardware Revision A1 (End-of-Life) contains a hardcoded telnet backdoor. The device starts a telnet daemon at boot via /bin/telnetd.sh with the username "Alphanetworks" and the static password "wrgn35_dlwbr_dir600l" read from /etc/alpha_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.
Title D-Link DIR-600L A1 Hardcoded Telnet Backdoor Credentials
First Time appeared Dlink
Dlink dir-600l Firmware
Weaknesses CWE-798
CPEs cpe:2.3:o:dlink:dir-600l_firmware:*:*:*:*:*:*:*:*
Vendors & Products Dlink
Dlink dir-600l Firmware
References
Metrics cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
securin
Published
Updated
May 5, 2026, 12:43 PM
Reserved
Apr 27, 2026, 6:21 AM
Status
Analyzed
Published
May 4, 2026, 5:16 PM
Modified
Oct 26, 2026, 7:10 PM