CVE-2026-42376

{
  "id": "CVE-2026-42376",
  "sourceIdentifier": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
  "published": "2026-05-04T17:16:26.000",
  "lastModified": "2026-10-26T19:10:00.163",
  "vulnStatus": "Analyzed",
  "cveTags": [
    {
      "sourceIdentifier": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
      "tags": [
        "unsupported-when-assigned"
      ]
    }
  ],
  "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."
    },
    {
      "lang": "es",
      "value": "D-Link DIR-456U Revisión de Hardware A1 (Fin de Vida Útil, FVU) contiene una puerta trasera telnet codificada de forma rígida. El dispositivo inicia un demonio telnet al arrancar a través de /etc/init0.d/S80telnetd.sh con el nombre de usuario ’Alphanetworks’ y la contraseña estática ’whdrv01_dlob_dir456U’ leída de /etc/config/image_sign. El binario telnetd personalizado acepta un indicador -u usuario:contraseña, y el binario de inicio de sesión personalizado utiliza strcmp() para validar las credenciales. La autenticación exitosa otorga a un atacante no autenticado en la red local un shell de root con control administrativo total. El dispositivo ha alcanzado el Fin de Vida Útil (FVU) y no recibirá parches."
    }
  ],
  "affected": [
    {
      "source": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
      "affectedData": [
        {
          "vendor": "D-Link",
          "product": "DIR-456U Firmware",
          "defaultStatus": "affected",
          "cpes": [
            "cpe:2.3:o:dlink:dir-456u_firmware:*:*:*:*:*:*:*:*"
          ],
          "platforms": [
            "MIPS32 Little-Endian"
          ],
          "versions": [
            {
              "version": "A1",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
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        "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
      }
    ],
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        "ssvcData": {
          "timestamp": "2026-05-04T16:32:05.738044Z",
          "id": "CVE-2026-42376",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-798"
        }
      ]
    }
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  "references": [
    {
      "url": "https://www.securin.io/zero-day/cve-2026-42376-hardcoded-telnet-backdoor-in-d-link-dir-456u-a1-end-of-life-",
      "source": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
      "tags": [
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        "Third Party Advisory"
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    {
      "url": "https://www.securin.io/zero-day/cve-2026-42376-hardcoded-telnet-backdoor-in-d-link-dir-456u-a1-end-of-life-",
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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}