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CVE-2026-54876

Estado: Pendiente de análisisAlta (7.5)—

Issue summary: A malicious TLS server can cause a memory leak in a TLS client that has enabled OCSP response checking by sending an OCSP response that contains no single response entries.

Impact summary: An attacker can leak an attacker-tunable amount of memory per TLS handshake in a victim client application. A long-running client that repeatedly connects to a malicious server can have its memory exhausted, resulting in a Denial of Service.

CWE: CWE-401: Missing Release of Memory after Effective Lifetime

Description: The affected function is called during X.509 certificate chain verification when OCSP response checking is enabled with the X509_V_FLAG_OCSP_RESP_CHECK or X509_V_FLAG_OCSP_RESP_CHECK_ALL verification flags, for example when a TLS client verifies an OCSP response stapled into the TLS handshake by the server.

Leer descripción completaMostrar menos

When the received BasicOCSPResponse contains an empty SEQUENCE OF SingleResponse, which is permitted on the wire and accepted by the OpenSSL decoder, the OCSP_BASICRESP structure allocated by OCSP_response_get1_basic() was not freed because an early return bypassed the cleanup code at the end of the function.

The amount of memory leaked per handshake can be amplified by the attacker by padding the certs field of the BasicOCSPResponse with bogus certificates, which are parsed and stored in the leaked structure before the empty response check triggers the early return. A long-running TLS client that repeatedly connects to a malicious server can have its memory exhausted over time.

OCSP response checking is not enabled by default. Only client applications that explicitly enable the OCSP response check verification flags are affected.

FIPS impact: no

The FIPS modules in 4.0 and 3.6 are not 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.

AV:N sin PR ni UI indica explotación remota de aplicación expuesta (T1190). La fuga de memoria causada por respuestas OCSP malformadas en handshakes TLS repetidos genera DoS por agotamiento de memoria (T1499.004), amplificable por padding de certificados.

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)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Openssl — OpensslAI

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-54876",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-54876",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-08-05T19:31:37.065781Z"
        }
      }
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    "cvssMetricV31": [
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          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.5,
          "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"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 3.9
      }
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  },
  "affected": [
    {
      "source": "openssl-security@openssl.org",
      "affectedData": [
        {
          "vendor": "OpenSSL",
          "product": "OpenSSL",
          "versions": [
            {
              "status": "affected",
              "version": "4.0.0",
              "lessThan": "4.0.2",
              "versionType": "semver"
            },
            {
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              "version": "3.6.0",
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  "published": "2026-08-05T15:16:53.487",
  "references": [
    {
      "url": "https://github.com/openssl/openssl/commit/155b5fe0f93365e6df1c56ee3606b121080c6c12",
      "source": "openssl-security@openssl.org"
    },
    {
      "url": "https://github.com/openssl/openssl/commit/d8c51048ac037a21bae0f41cad7a3920dc7f3638",
      "source": "openssl-security@openssl.org"
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    {
      "url": "https://openssl-library.org/news/secadv/20260805.txt",
      "source": "openssl-security@openssl.org"
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      "url": "http://www.openwall.com/lists/oss-security/2026/08/05/8",
      "source": "af854a3a-2127-422b-91ae-364da2661108"
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  "vulnStatus": "Awaiting Analysis",
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      "type": "Secondary",
      "source": "openssl-security@openssl.org",
      "description": [
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  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Issue summary: A malicious TLS server can cause a memory leak in a TLS\nclient that has enabled OCSP response checking by sending an OCSP\nresponse that contains no single response entries.\n\nImpact summary: An attacker can leak an attacker-tunable amount of memory\nper TLS handshake in a victim client application. A long-running client\nthat repeatedly connects to a malicious server can have its memory\nexhausted, resulting in a Denial of Service.\n\nCWE: CWE-401: Missing Release of Memory after Effective Lifetime\n\nDescription: The affected function is called during X.509 certificate\nchain verification when OCSP response checking is enabled\nwith the X509_V_FLAG_OCSP_RESP_CHECK or X509_V_FLAG_OCSP_RESP_CHECK_ALL\nverification flags, for example when a TLS client verifies an OCSP\nresponse stapled into the TLS handshake by the server.\n\nWhen the received BasicOCSPResponse contains an empty SEQUENCE OF\nSingleResponse, which is permitted on the wire and accepted by the\nOpenSSL decoder, the OCSP_BASICRESP structure allocated by\nOCSP_response_get1_basic() was not freed because an early return\nbypassed the cleanup code at the end of the function.\n\nThe amount of memory leaked per handshake can be amplified by the\nattacker by padding the certs field of the BasicOCSPResponse with\nbogus certificates, which are parsed and stored in the leaked\nstructure before the empty response check triggers the early return.\nA long-running TLS client that repeatedly connects to a malicious\nserver can have its memory exhausted over time.\n\nOCSP response checking is not enabled by default. Only client\napplications that explicitly enable the OCSP response check\nverification flags are affected.\n\nFIPS impact: no\n\nThe FIPS modules in 4.0 and 3.6 are not affected by this issue as the\naffected code is outside the OpenSSL FIPS module boundary."
    }
  ],
  "lastModified": "2026-08-28T19:46:29.323",
  "sourceIdentifier": "openssl-security@openssl.org"
}