Vulnerability · Published May 4, 2026 · Assigned by securin

CVE-2026-42375D-Link DIR-600L A1 Hardcoded Telnet Backdoor Credentials

Critical 9.8

In plain English

A critical-severity hard-coded credentials in DIR-600L Firmware from D-Link. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities).

Severity (CVSS 3.1)9.8Critical

Exploit odds (30 days)0.5%top 59.0% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
D-Link	DIR-600L Firmware	A1

Weakness: CWE-798 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References

D-Link DIR-600L A1 Hardcoded Telnet Backdoor - Securin Advisory