CVE-2026-50046

{
  "id": "CVE-2026-50046",
  "sourceIdentifier": "[email protected]",
  "published": "2026-07-22T14:17:20.117",
  "lastModified": "2026-10-24T13:10:00.147",
  "vulnStatus": "Analyzed",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In NLnet Labs Unbound 1.15.0 up to and including 1.25.1, the TLS server name used for DNS-over-TLS (DoT) forwarded queries is tied to a struct's ('serviced_query') lifetime but also referenced by another struct ('waiting_tcp'). When the owning struct is jostled out of the mesh while the DoT TCP stream is still handshaking it frees the storage behind the referenced string and if the TLS stream then errors out, it dereferences the freed pointer. The dereference is read-only and the practical impact is a daemon crash resulting in denial of service. A malicious actor that knows a DoT forwarding/stub Unbound's configuration could exploit the vulnerability by quering records in the appropriate zone while keeping Unbound uder pressure so that the jostle logic kicks in. If answers for the vulnerable zone are slow, the likelihood of jostling such queries is higher, although the timing of the jostle needs to be precise. Requirements for a vulnerable Unbound is the existence of a stub/forward zone configured for DoT together with a configured '#authname' suffix on the server identification. The connectivity to the server needs to exhibit a transient failure at the correct time in order to kick off the vulnerable error path."
    },
    {
      "lang": "es",
      "value": "En NLnet Labs Unbound 1.15.0 hasta la versión 1.25.1 inclusive, el nombre del servidor TLS utilizado para consultas reenviadas de DNS-over-TLS (DoT) está vinculado al ciclo de vida de una estructura (’serviced_query’) pero también referenciado por otra estructura (’waiting_tcp’). Cuando la estructura propietaria es desalojada de la malla mientras el flujo TCP de DoT aún está realizando el ’handshake’, libera el almacenamiento detrás de la cadena referenciada y, si el flujo TLS luego falla, desreferencia el puntero liberado. La desreferencia es de solo lectura y el impacto práctico es un fallo del demonio que resulta en denegación de servicio. Un actor malicioso que conoce la configuración de un Unbound de reenvío/stub de DoT podría explotar la vulnerabilidad consultando registros en la zona apropiada mientras mantiene a Unbound bajo presión para que la lógica de desalojo se active. Si las respuestas para la zona vulnerable son lentas, la probabilidad de desalojar dichas consultas es mayor, aunque el momento del desalojo debe ser preciso. Los requisitos para un Unbound vulnerable son la existencia de una zona stub/forward configurada para DoT junto con un sufijo ’#authname’ configurado en la identificación del servidor. La conectividad al servidor necesita exhibir un fallo transitorio en el momento correcto para activar la ruta de error vulnerable."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "NLnet Labs",
          "product": "Unbound",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "1.15.0",
              "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:H",
          "baseScore": 5.9,
          "baseSeverity": "MEDIUM",
          "attackVector": "NETWORK",
          "attackComplexity": "HIGH",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 3.6
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-07-22T18:57:24.481710Z",
          "id": "CVE-2026-50046",
          "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-416"
        }
      ]
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "operator": "OR",
          "negate": false,
          "cpeMatch": [
            {
              "vulnerable": true,
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              "versionStartIncluding": "1.15.0",
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  "references": [
    {
      "url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-50046.txt",
      "source": "[email protected]",
      "tags": [
        "Vendor Advisory"
      ]
    }
  ]
}