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.
"}],"value":"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."}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":9.8,"baseSeverity":"CRITICAL","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-798","description":"CWE-798 Use of Hard-coded Credentials","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-05-04T16:02:17.044Z","orgId":"33c584b5-0579-4c06-b2a0-8d8329fcab9c","shortName":"securin"},"references":[{"name":"D-Link DIR-600L A1 Hardcoded Telnet Backdoor - Securin Advisory","url":"https://www.securin.io/zero-day/cve-2026-42375-hardcoded-telnet-backdoor-in-d-link-dir-600l-a1-end-of-life-"}],"source":{"discovery":"EXTERNAL"},"tags":["unsupported-when-assigned"],"title":"D-Link DIR-600L A1 Hardcoded Telnet Backdoor Credentials","workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"This product is End-of-Life 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).
"}],"value":"This product is End-of-Life 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)."}],"x_generator":{"engine":"Vulnogram 1.0.2"}}},"cveMetadata":{"assignerOrgId":"33c584b5-0579-4c06-b2a0-8d8329fcab9c","assignerShortName":"securin","cveId":"CVE-2026-42375","datePublished":"2026-05-04T16:02:17.044Z","dateReserved":"2026-04-27T06:21:56.902Z","dateUpdated":"2026-05-05T12:43:07.508Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-05-04 17:16:25","lastModifiedDate":"2026-05-06 12:17:37","problem_types":["CWE-798","CWE-798 CWE-798 Use of Hard-coded Credentials"],"metrics":{"cvssMetricV31":[{"source":"33c584b5-0579-4c06-b2a0-8d8329fcab9c","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":5.9},{"source":"nvd@nist.gov","type":"Primary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":8.8,"baseSeverity":"HIGH","attackVector":"ADJACENT_NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":2.8,"impactScore":5.9}]},"configurations":[{"operator":"AND","nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:dlink:dir-600l_firmware:*:*:*:*:*:*:*:*","matchCriteriaId":"585AD6F9-C845-430D-B77B-7463872EAD98"}]},{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":false,"criteria":"cpe:2.3:h:dlink:dir-600l:a1:*:*:*:*:*:*:*","matchCriteriaId":"F75E7D9C-03BE-4301-AF9E-9929C33F4EEA"}]}]}]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"42375","Ordinal":"1","Title":"D-Link DIR-600L A1 Hardcoded Telnet Backdoor Credentials","CVE":"CVE-2026-42375","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"42375","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"D-Link DIR-600L A1 Hardcoded Telnet Backdoor Credentials"}]}}}