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CVE-2026-42765

Estado: AnalizadaAlta (7.5)—

Issue summary: When a partial-chain certificate verification is enabled together with OCSP response checking for the whole chain, a NULL dereference will happen if the verified chain does not have a self-signed trusted anchor, crashing the process.

Impact summary: A NULL pointer dereference can trigger a crash which leads to a Denial of Service for an application.

When performing OCSP response checking for certificates in the verification chain, the code always tries to access the next certificate as the issuer. There is a check for a self-signed certificate. However with the partial chain verification enabled when the chain does not have a self-signed trusted anchor, the issuer will be NULL for the last certificate in the chain. A NULL pointer dereference then happens.

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This issue affects only applications which enable both OCSP verification of the certificate chain (X509_V_FLAG_OCSP_RESP_CHECK_ALL) and partial chain verification (X509_V_FLAG_PARTIAL_CHAIN) in the certificate verification. Both flags are disabled by default. For that reason, we have assigned Low severity to the issue.

No FIPS modules are affected by this issue as the affected code is outside the OpenSSL FIPS module boundary.

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

Vulnerabilidad de red sin autenticación (AV:N/PR:N) que causa NULL dereference en OpenSSL con flags OCSP+partial-chain habilitados, crasheando el proceso (A:H) y originando DoS de aplicación.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Filter Network TrafficVulnerability ScanningPrivileged Account ManagementNetwork SegmentationLimit Access to Resource Over NetworkApplication Isolation and Sandboxing

Tecnologías afectadas (1)

Openssl — Openssl

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-42765",
  "cveTags": [],
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          "id": "CVE-2026-42765",
          "role": "CISA Coordinator",
          "options": [
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              "exploitation": "none"
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              "automatable": "yes"
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              "technicalImpact": "partial"
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          "version": "2.0.3",
          "timestamp": "2026-06-09T19:35:48.849695Z"
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          "version": "3.1",
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          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
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  "affected": [
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      "source": "openssl-security@openssl.org",
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          "product": "OpenSSL",
          "versions": [
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  "published": "2026-06-09T17:17:07.843",
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      "url": "https://github.com/openssl/openssl/commit/14340b7fa1d444615486bc137014b064e64ec334",
      "tags": [
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      "source": "openssl-security@openssl.org"
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    {
      "url": "https://github.com/openssl/openssl/commit/eb345da18ce2216b2f3ade9c2bc23e068487fa97",
      "tags": [
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      "source": "openssl-security@openssl.org"
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      "url": "https://openssl-library.org/news/secadv/20260609.txt",
      "tags": [
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      "source": "openssl-security@openssl.org"
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  "weaknesses": [
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      "type": "Secondary",
      "source": "openssl-security@openssl.org",
      "description": [
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          "value": "CWE-476"
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      ]
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  "descriptions": [
    {
      "lang": "en",
      "value": "Issue summary: When a partial-chain certificate verification is enabled\ntogether with OCSP response checking for the whole chain, a NULL dereference\nwill happen if the verified chain does not have a self-signed trusted anchor,\ncrashing the process.\n\nImpact summary: A NULL pointer dereference can trigger a crash which leads to a\nDenial of Service for an application.\n\nWhen performing OCSP response checking for certificates in the verification\nchain, the code always tries to access the next certificate as the issuer.\nThere is a check for a self-signed certificate. However with the partial\nchain verification enabled when the chain does not have a self-signed trusted\nanchor, the issuer will be NULL for the last certificate in the chain. A NULL\npointer dereference then happens.\n\nThis issue affects only applications which enable both OCSP verification\nof the certificate chain (X509_V_FLAG_OCSP_RESP_CHECK_ALL) and partial\nchain verification (X509_V_FLAG_PARTIAL_CHAIN) in the certificate\nverification. Both flags are disabled by default. For that reason, we have\nassigned Low severity to the issue.\n\nNo FIPS modules are affected by this issue as the affected code is outside\nthe OpenSSL FIPS module boundary."
    },
    {
      "lang": "es",
      "value": "Resumen del problema: Cuando la verificación de certificado de cadena parcial está habilitada junto con la comprobación de respuesta OCSP para toda la cadena, ocurrirá una desreferencia de NULL si la cadena verificada no tiene un ancla de confianza autofirmada, bloqueando el proceso.\n\nResumen del impacto: Una desreferencia de puntero NULL puede desencadenar un bloqueo que lleva a una Denegación de Servicio para una aplicación.\n\nAl realizar la comprobación de respuesta OCSP para certificados en la cadena de verificación, el código siempre intenta acceder al siguiente certificado como emisor. Hay una comprobación para un certificado autofirmado. Sin embargo, con la verificación de cadena parcial habilitada, cuando la cadena no tiene un ancla de confianza autofirmada, el emisor será NULL para el último certificado de la cadena. Entonces ocurre una desreferencia de puntero NULL.\n\nEste problema afecta solo a las aplicaciones que habilitan tanto la verificación OCSP de la cadena de certificados (X509_V_FLAG_OCSP_RESP_CHECK_ALL) como la verificación de cadena parcial (X509_V_FLAG_PARTIAL_CHAIN) en la verificación de certificados. Ambas banderas están deshabilitadas por defecto. Por esa razón, hemos asignado una severidad Baja al problema.\n\nNingún módulo FIPS se ve afectado por este problema ya que el código afectado está fuera del límite del módulo FIPS de OpenSSL."
    }
  ],
  "lastModified": "2026-07-23T08:10:00.137",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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              "criteria": "cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*",
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