{"id":"CVE-2026-42376","state":"PUBLISHED","title":"D-Link DIR-456U A1 Hardcoded Telnet Backdoor Credentials","description":"D-Link DIR-456U Hardware Revision A1 (End-of-Life, EOL) contains a hardcoded telnet backdoor. The device starts a telnet daemon at boot via /etc/init0.d/S80telnetd.sh with the username \"Alphanetworks\" and the static password \"whdrv01_dlob_dir456U\" read from /etc/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.","publishedAt":"2026-05-04T16:03:59.473Z","updatedAt":"2026-05-04T16:32:10.149Z","severity":{"score":9.8,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"securin"},"assigner":"securin","products":["D-Link DIR-456U Firmware"],"affected":[{"vendor":"D-Link","product":"DIR-456U Firmware","defaultStatus":"affected","versions":[{"version":"A1","status":"affected","versionType":"custom"}],"platforms":["MIPS32 Little-Endian"],"cpes":["cpe:2.3:o:dlink:dir-456u_firmware:*:*:*:*:*:*:*:*"]}],"references":["https://www.securin.io/zero-day/cve-2026-42376-hardcoded-telnet-backdoor-in-d-link-dir-456u-a1-end-of-life-"],"weaknesses":["CWE-798"],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/42xxx/CVE-2026-42376.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-42376","state":"PUBLISHED","datePublished":"2026-05-04T16:03:59.473Z","dateUpdated":"2026-05-04T16:32:10.149Z","assignerShortName":"securin","assignerOrgId":"33c584b5-0579-4c06-b2a0-8d8329fcab9c","dateReserved":"2026-04-27T06:21:56.902Z"},"containers":{"cna":{"title":"D-Link DIR-456U A1 Hardcoded Telnet Backdoor Credentials","descriptions":[{"lang":"en","value":"D-Link DIR-456U Hardware Revision A1 (End-of-Life, EOL) contains a hardcoded telnet backdoor. The device starts a telnet daemon at boot via /etc/init0.d/S80telnetd.sh with the username \"Alphanetworks\" and the static password \"whdrv01_dlob_dir456U\" read from /etc/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."}],"affected":[{"vendor":"D-Link","product":"DIR-456U Firmware","defaultStatus":"affected","versions":[{"version":"A1","status":"affected","versionType":"custom"}],"platforms":["MIPS32 Little-Endian"],"cpes":["cpe:2.3:o:dlink:dir-456u_firmware:*:*:*:*:*:*:*:*"]}],"references":[{"url":"https://www.securin.io/zero-day/cve-2026-42376-hardcoded-telnet-backdoor-in-d-link-dir-456u-a1-end-of-life-","name":"D-Link DIR-456U A1 Hardcoded Telnet Backdoor - Securin Advisory"}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV3_1":{"version":"3.1","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH","baseSeverity":"CRITICAL","baseScore":9.8,"vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-798","lang":"en","description":"CWE-798 Use of Hard-coded Credentials","type":"CWE"}]}],"providerMetadata":{"shortName":"securin","orgId":"33c584b5-0579-4c06-b2a0-8d8329fcab9c","dateUpdated":"2026-05-04T16:03:59.473Z"},"datePublic":"2026-04-24T00:00:00.000Z","tags":["unsupported-when-assigned"],"workarounds":[{"lang":"en","value":"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).","supportingMedia":[{"type":"text/html","base64":false,"value":"<p>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).</p>"}]}],"credits":[{"lang":"en","value":"Arjun Basnet from Securin Labs","type":"finder"}],"source":{"discovery":"EXTERNAL"},"x_generator":{"engine":"Vulnogram 1.0.2"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://www.securin.io/zero-day/cve-2026-42376-hardcoded-telnet-backdoor-in-d-link-dir-456u-a1-end-of-life-","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-05-04T16:32:05.738044Z","id":"CVE-2026-42376","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-05-04T16:32:10.149Z"}}]}}}