CVE-2026-44687

{
  "id": "CVE-2026-44687",
  "sourceIdentifier": "[email protected]",
  "published": "2026-07-22T14:17:19.040",
  "lastModified": "2026-10-24T13:10:00.147",
  "vulnStatus": "Analyzed",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In NLnet Labs Unbound 1.13.2 up to and including 1.25.1, stub or forward zones where the name is below an intermediate labed below a DNSSEC signed zone could be shadowed by the intermediate label's secure NXDOMAIN answer from the parent. This is caused by an off-by-one error in 'harden-below-nxdomain' logic; enabled by default. It effectively bypasses the configuration and the configured stub/forward zone is never contacted. 'harden-below-nxdomain' does an upward DNS cache walk together with a delegation point guard that does not allow NXDOMAIN synthesis above stub/forward zones. The guard tests the domain name but before stripping a label. This results in an iteration where the domain name equals the configured stub/forward zone apex that passes the guard, strips one more label, and probes the cache at the apex's immediate public parent. If that parent has a cached DNSSEC-secure NXDOMAIN, which it will for any private namespace nested two or more labels under a signed public name, the walk returns it and the configured stub/forward upstream is never contacted. This can only be triggered by the query for the intermediate label (between the stub/forward apex and the DNSSEC parent zone)."
    },
    {
      "lang": "es",
      "value": "En NLnet Labs Unbound 1.13.2 hasta la 1.25.1 inclusive, las zonas stub o de reenvío donde el nombre está por debajo de una etiqueta intermedia que a su vez está por debajo de una zona firmada con DNSSEC podrían ser ensombrecidas por la respuesta NXDOMAIN segura de la etiqueta intermedia proveniente del padre. Esto es causado por un error de desplazamiento de uno en la lógica de ’harden-below-nxdomain’; habilitado por defecto. Efectivamente, esto elude la configuración y la zona stub/de reenvío configurada nunca es contactada. ’harden-below-nxdomain’ realiza un recorrido ascendente de la caché DNS junto con un guardián de punto de delegación que no permite la síntesis de NXDOMAIN por encima de las zonas stub/de reenvío. El guardián prueba el nombre de dominio pero antes de eliminar una etiqueta. Esto resulta en una iteración donde el nombre de dominio es igual al ápice de la zona stub/de reenvío configurada que pasa el guardián, elimina una etiqueta más y sondea la caché en el padre público inmediato del ápice. Si ese padre tiene un NXDOMAIN seguro con DNSSEC en caché, lo cual ocurrirá para cualquier espacio de nombres privado anidado dos o más etiquetas por debajo de un nombre público firmado, el recorrido lo devuelve y el upstream stub/de reenvío configurado nunca es contactado. Esto solo puede ser provocado por la consulta para la etiqueta intermedia (entre el ápice stub/de reenvío y la zona padre DNSSEC)."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "NLnet Labs",
          "product": "Unbound",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "1.13.2",
              "lessThan": "1.25.2",
              "versionType": "semver",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
          "baseScore": 3.7,
          "baseSeverity": "LOW",
          "attackVector": "NETWORK",
          "attackComplexity": "HIGH",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "availabilityImpact": "LOW"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 1.4
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-07-22T14:19:38.843549Z",
          "id": "CVE-2026-44687",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-193"
        }
      ]
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "operator": "OR",
          "negate": false,
          "cpeMatch": [
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "1.13.2",
              "versionEndExcluding": "1.25.2",
              "matchCriteriaId": "0694F190-599A-4953-9758-0155C53510E2"
            }
          ]
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-44687.txt",
      "source": "[email protected]",
      "tags": [
        "Vendor Advisory"
      ]
    }
  ]
}