D-Link DIR-605L B2 /bin/telnetd.sh strcmp hard-coded credentials

Summaryinfo

A vulnerability described as critical has been identified in D-Link DIR-605L B2. Affected by this issue is the function strcmp of the file /bin/telnetd.sh. Executing a manipulation can lead to hard-coded credentials. This vulnerability only affects products that are no longer supported by the maintainer. This vulnerability appears as CVE-2026-42373. The attacker needs to be present on the local network. There is no available exploit.

Detailsinfo

A vulnerability was found in D-Link DIR-605L B2 (unknown version). It has been declared as critical. This vulnerability affects the function strcmp of the file /bin/telnetd.sh. The manipulation with an unknown input leads to a hard-coded credentials vulnerability. The CWE definition for the vulnerability is 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. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

D-Link DIR-605L Hardware Revision B2 (End-of-Life, EOL) 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 "wrgn76_dlwbr_dir605L" 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 presented by Arjun Basnet. The advisory is shared for download at securin.io. This vulnerability was named CVE-2026-42373 since 04/27/2026. The exploitation appears to be easy. Access to the local network is required for this attack. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $5k-$25k (estimation calculated on 05/04/2026). The MITRE ATT&CK project declares the attack technique as T1110.001.

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

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-27023). Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

• Router Operating System

Vendor

• D-Link

Name

• DIR-605L B2

License

• commercial

Support

• end of life

Website

• Vendor: https://www.dlink.com/

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Once again VulDB remains the best source for vulnerability data.

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