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CVE-2026-71889

Estado: RecibidaAlta (8.7)—

In Bouncy Castle for Java before 1.86, neither copy of PKIXCertPathReviewer - org.bouncycastle.pkix.jcajce.PKIXCertPathReviewer nor the legacy org.bouncycastle.x509.PKIXCertPathReviewer - applied X.509 name constraints to the end-entity certificate. checkNameConstraints walked the path with a loop bound of index greater than zero, which is the bound the CA-only steps require, but index zero is the target certificate under the standard CertPath ordering, so the permitted and excluded subtree checks of RFC 5280 sec. 6.1.3 (b) and (c) never ran against the leaf's subject DN or its subjectAltName.

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A chain whose leaf violated a NameConstraints extension imposed by its own issuing CA therefore reported isValidCertPath() true with an empty error list, while CertPathValidator.getInstance("PKIX", "BC"), which shares no code with the reviewer, rejected the identical chain against the identical trust anchor. An application using the reviewer to make the trust decision rather than for diagnostics alongside a real validation accepted a certificate the constrained CA was never authorised to issue. Both copies now check every certificate in the path including the target, waive the sec. 4.2.1.10 self-issued exemption for the final certificate as sec. 6.1.3 requires, and skip the sec. 6.1.4 (g) constraint-accumulation step for the target. This issue also affects Bouncy Castle for Java LTS before 2.73.13, which carries only the org.bouncycastle.pkix.jcajce copy of the reviewer. It also affects Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 1.0.13 (1.0.X series), 2.0.13 (2.0.X series) and 2.1.13 (2.1.X series).

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.

La vulnerabilidad permite a un atacante remoto presentar cadenas de certificados falsas que violarían restricciones X.509 pero serían aceptadas como válidas (VI:H), permitiendo suplantación de identidad (man-in-the-middle) sin validación correcta de restricciones de nombre.

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

Network SegmentationLimit Access to Resource Over NetworkFilter Network TrafficVulnerability ScanningUser TrainingPrivileged Account Management

Tecnologías afectadas (1)

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

Bouncycastle — BouncycastleAI

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-71889",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-71889",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-10-05T16:55:41.462500Z"
        }
      }
    ],
    "cvssMetricV40": [
      {
        "type": "Secondary",
        "source": "91579145-5d7b-4cc5-b925-a0262ff19630",
        "cvssData": {
          "Safety": "NOT_DEFINED",
          "version": "4.0",
          "Recovery": "NOT_DEFINED",
          "baseScore": 8.7,
          "Automatable": "NOT_DEFINED",
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber",
          "exploitMaturity": "NOT_DEFINED",
          "providerUrgency": "AMBER",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "privilegesRequired": "NONE",
          "subIntegrityImpact": "NONE",
          "vulnIntegrityImpact": "HIGH",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "vulnAvailabilityImpact": "NONE",
          "availabilityRequirement": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "subConfidentialityImpact": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "confidentialityRequirement": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED"
        }
      }
    ]
  },
  "affected": [
    {
      "source": "91579145-5d7b-4cc5-b925-a0262ff19630",
      "affectedData": [
        {
          "repo": "https://github.com/bcgit/bc-java",
          "vendor": "Legion of the Bouncy Castle Inc.",
          "modules": [
            "pkix"
          ],
          "product": "BC-JAVA",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "lessThan": "1.86",
              "versionType": "maven"
            }
          ],
          "platforms": [
            "all"
          ],
          "packageURL": "pkg:maven/org.bouncycastle/bcpkix-jdk18on",
          "packageName": "bcpkix",
          "programFiles": [
            "PKIXCertPathReviewer"
          ],
          "collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java/",
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://github.com/bcgit/bc-java",
          "vendor": "Legion of the Bouncy Castle Inc.",
          "modules": [
            "prov"
          ],
          "product": "BC-JAVA",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "lessThan": "1.86",
              "versionType": "maven"
            }
          ],
          "platforms": [
            "all"
          ],
          "packageURL": "pkg:maven/org.bouncycastle/bcprov-jdk18on",
          "packageName": "bcprov",
          "programFiles": [
            "PKIXCertPathReviewer"
          ],
          "collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java/",
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://github.com/bcgit/bc-lts-java",
          "vendor": "Legion of the Bouncy Castle Inc.",
          "modules": [
            "pkix"
          ],
          "product": "BC-LTS-JAVA",
          "versions": [
            {
              "status": "affected",
              "version": "2.73.0",
              "lessThan": "2.73.13",
              "versionType": "maven"
            }
          ],
          "platforms": [
            "all"
          ],
          "packageURL": "pkg:maven/org.bouncycastle/bcpkix-lts8on",
          "packageName": "bcpkix-lts8on",
          "programFiles": [
            "PKIXCertPathReviewer"
          ],
          "collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java-lts/",
          "defaultStatus": "unaffected"
        },
        {
          "vendor": "Legion of the Bouncy Castle Inc.",
          "product": "BC-FJA",
          "versions": [
            {
              "status": "affected",
              "version": "1.0.4",
              "lessThan": "1.0.13",
              "versionType": "maven"
            },
            {
              "status": "affected",
              "version": "2.0.0",
              "lessThan": "2.0.13",
              "versionType": "maven"
            },
            {
              "status": "affected",
              "version": "2.1.0",
              "lessThan": "2.1.13",
              "versionType": "maven"
            }
          ],
          "platforms": [
            "all"
          ],
          "packageURL": "pkg:maven/org.bouncycastle/bcpkix-fips",
          "packageName": "bcpkix-fips",
          "collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java-fips/",
          "defaultStatus": "unaffected"
        }
      ]
    }
  ],
  "published": "2026-10-03T09:17:05.437",
  "references": [
    {
      "url": "https://github.com/bcgit/bc-java/commit/06dcff2f51037095de126986285c998e3455ab85",
      "source": "91579145-5d7b-4cc5-b925-a0262ff19630"
    },
    {
      "url": "https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9071889",
      "source": "91579145-5d7b-4cc5-b925-a0262ff19630"
    }
  ],
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "91579145-5d7b-4cc5-b925-a0262ff19630",
      "description": [
        {
          "lang": "en",
          "value": "CWE-295"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "In Bouncy Castle for Java before 1.86, neither copy of PKIXCertPathReviewer - org.bouncycastle.pkix.jcajce.PKIXCertPathReviewer nor the legacy org.bouncycastle.x509.PKIXCertPathReviewer - applied X.509 name constraints to the end-entity certificate. checkNameConstraints walked the path with a loop bound of index greater than zero, which is the bound the CA-only steps require, but index zero is the target certificate under the standard CertPath ordering, so the permitted and excluded subtree checks of RFC 5280 sec. 6.1.3 (b) and (c) never ran against the leaf's subject DN or its subjectAltName. A chain whose leaf violated a NameConstraints extension imposed by its own issuing CA therefore reported isValidCertPath() true with an empty error list, while CertPathValidator.getInstance(\"PKIX\", \"BC\"), which shares no code with the reviewer, rejected the identical chain against the identical trust anchor. An application using the reviewer to make the trust decision rather than for diagnostics alongside a real validation accepted a certificate the constrained CA was never authorised to issue. Both copies now check every certificate in the path including the target, waive the sec. 4.2.1.10 self-issued exemption for the final certificate as sec. 6.1.3 requires, and skip the sec. 6.1.4 (g) constraint-accumulation step for the target. This issue also affects Bouncy Castle for Java LTS before 2.73.13, which carries only the org.bouncycastle.pkix.jcajce copy of the reviewer. It also affects Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 1.0.13 (1.0.X series), 2.0.13 (2.0.X series) and 2.1.13 (2.1.X series)."
    }
  ],
  "lastModified": "2026-10-05T17:17:15.857",
  "sourceIdentifier": "91579145-5d7b-4cc5-b925-a0262ff19630"
}