D-Link DIR-605L B2 Hardcoded Telnet Backdoor Credentials

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Summary

CVECVE-2026-42373
StatePUBLISHED
Assignersecurin
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-04 17:16:25 UTC
Updated2026-05-06 12:19:20 UTC
DescriptionD-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.

Risk And Classification

Primary CVSS: v3.1 8.8 HIGH from [email protected]

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.000610000 probability, percentile 0.188450000 (date 2026-05-05)

Problem Types: CWE-798 | CWE-798 CWE-798 Use of Hard-coded Credentials

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary8.8HIGHCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.133c584b5-0579-4c06-b2a0-8d8329fcab9cSecondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNACVSS9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Adjacent
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Hardware Dlink Dir-605l b2 All All All
Operating System Dlink Dir-605l Firmware All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA D-Link DIR-605L Firmware affected B2 custom MIPS32 Big-Endian

References

ReferenceSourceLinkTags
www.securin.io/zero-day/cve-2026-42373-hardcoded-telnet-backdoor-in-d-link-d... 134c704f-9b21-4f2e-91b3-4a467353bcc0 www.securin.io Exploit, Third Party Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Arjun Basnet from Securin Labs (en)

Additional Advisory Data

Workarounds

CNA: This product is End-of-Life (EOL) 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).

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