D-Link DIR-600L A1 /bin/telnetd.sh strcmp hard-coded credentials

Summaryinfo

A vulnerability classified as critical was found in D-Link DIR-600L A1. This vulnerability affects the function strcmp of the file /bin/telnetd.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-2026-42375. Access to the local network is required for this attack. No exploit is available.

Detailsinfo

A vulnerability classified as critical has been found in D-Link DIR-600L A1 (version unknown). Affected is the function strcmp of the file /bin/telnetd.sh. The manipulation with an unknown input leads to a hard-coded credentials vulnerability. CWE is classifying the issue as CWE-798. The product contains hard-coded credentials, such as a password or cryptographic key, which it uses for its own inbound authentication, outbound communication to external components, or encryption of internal data. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

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.

The weakness was published by Arjun Basnet. The advisory is available at securin.io. This vulnerability is traded as CVE-2026-42375 since 04/27/2026. The exploitability is told to be easy. The attack needs to approached within the local network. The exploitation doesn't require any form of authentication. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $5k-$25k at the moment (estimation calculated on 05/04/2026). This vulnerability is assigned to T1110.001 by the MITRE ATT&CK project.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Type

• Router Operating System

Vendor

• D-Link

Name

• DIR-600L A1

License

• commercial

Support

• end of life

Website

• Vendor: https://www.dlink.com/

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