CVE-2026-42372
Published: 04 May 2026
Summary
CVE-2026-42372 is a high-severity Use of Hard-coded Credentials (CWE-798) vulnerability in Dlink Dir-605L Firmware. Its CVSS base score is 8.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Remote Services (T1021); ranked at the 15.6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
This vulnerability is AI-related — categorised as Other AI Platforms.
The strongest mitigations our analysis identified are NIST 800-53 SA-22 (Unsupported System Components) and SC-7 (Boundary Protection).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Directly prohibits or restricts the use of unsupported end-of-life devices like the DIR-605L, preventing exploitation of unpatchable hardcoded telnet backdoors.
Monitors and controls communications at network boundaries to block adjacent network access to the telnet daemon on port 23.
Enables monitoring for indicators of compromise such as unauthorized telnet connections or anomalous root shell activity from the backdoor.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Hardcoded telnet credentials directly enable Valid Accounts (default/backdoor account T1078.001) to access Remote Services (telnet T1021) and obtain a root Unix shell (T1059.004).
NVD Description
D-Link DIR-605L Hardware Revision A1 (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 "wrgn35_dlwbr_dir605l" read from /etc/alpha_config/image_sign. The custom telnetd binary accepts a…
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-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.
Deeper analysisAI
CVE-2026-42372 is a hardcoded credentials vulnerability (CWE-798) affecting the D-Link DIR-605L Hardware Revision A1 router, an End-of-Life (EOL) device. The flaw involves a telnet backdoor that starts a telnet daemon at boot via the /bin/telnetd.sh script. This daemon uses hardcoded credentials—username "Alphanetworks" and static password "wrgn35_dlwbr_dir605l"—sourced from /etc/alpha_config/image_sign. A custom telnetd binary accepts a -u user:password flag, while the custom login binary employs strcmp() for credential validation. The vulnerability carries a CVSS v3.1 base score of 8.8 (AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).
An unauthenticated attacker on the local network (adjacent access) can exploit this backdoor with low complexity and no privileges required. By connecting to the telnet service and supplying the known credentials, the attacker gains a root shell, achieving full administrative control over the device, including high confidentiality, integrity, and availability impacts.
Advisories, including those from Securin.io, confirm the device is EOL and will not receive patches or firmware updates for mitigation. Security practitioners should isolate or decommission affected DIR-605L A1 routers, as no vendor remediation is available. References: https://www.securin.io/zero-day/cve-2026-42372-hardcoded-telnet-backdoor-in-d-link-dir-605l-a1-end-of-life-.
Details
- CWE(s)
Affected Products
AI Security AnalysisAI
- AI Category
- Other AI Platforms
- Risk Domain
- N/A
- OWASP Top 10 for LLMs 2025
- None mapped
- Classification Reason
- Matched keywords: backdoor