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CVE-2026-71888

Estado: Pendiente de análisisAlta (8.7)—

In Bouncy Castle for Java before 1.86, the streaming CMS AuthenticatedData parser accepted a message whose digestAlgorithm and authAttrs fields disagreed about whether authenticated attributes were present. RFC 5652 sec. 9.1 pairs the two, requiring that authAttrs be present whenever digestAlgorithm is, and sec. 9.2 makes the MAC cover the DER encoding of authAttrs when they are present and the eContent OCTET STRING directly when they are not.

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CMSAuthenticatedDataParser has to choose between those two in its constructor, before it can reach authAttrs, which comes later in the SEQUENCE, so it chose on digestAlgorithm alone: for a message with digestAlgorithm absent but authAttrs present it verified the content MAC and then returned the attributes through getAuthAttrs() as though they had been authenticated, when the MAC had never covered them. An attacker able to modify a message in transit could insert an authenticated attribute, such as an RFC 2634 ESSSecurityLabel, into an otherwise valid message while holding neither the key-encryption key nor the content-MAC key, and an application taking an authorization, routing or labelling decision from those attributes would act on attacker-chosen values. The content itself remained MAC-bound. asn1.cms.AuthenticatedData now rejects the mismatched pairing when parsing and CMSAuthenticatedDataParser cross-checks the two fields once authAttrs is read. This is a variant of CVE-2026-59642, which bound the content to the MAC for messages that legitimately carry authAttrs, and which does not address this case. This issue also affects Bouncy Castle for Java LTS before 2.73.13, and 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), and bcutil-fips 2.0.8 (2.0.X series) and 2.1.8 (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.

Parser CMS acepta mensajes con digestAlgorithm y authAttrs inconsistentes, permitiendo insertar atributos autenticados sin poseer claves (VI:H indica modificación de integridad remota sin privilegios).

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

Restrict File and Directory PermissionsVulnerability ScanningUser TrainingPrivileged Account ManagementPassword PoliciesRemote Data Storage

Tecnologías afectadas (1)

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

Bouncycastle — Bouncy CastleAI

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-71888",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-71888",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-10-05T16:51:49.725826Z"
        }
      }
    ],
    "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": [
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              "status": "affected",
              "version": "0",
              "lessThan": "1.86",
              "versionType": "maven"
            }
          ],
          "platforms": [
            "all"
          ],
          "packageURL": "pkg:maven/org.bouncycastle/bcpkix-jdk18on",
          "packageName": "bcpkix",
          "programFiles": [
            "CMSAuthenticatedDataParser"
          ],
          "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": [
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              "status": "affected",
              "version": "1.70",
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            }
          ],
          "platforms": [
            "all"
          ],
          "packageURL": "pkg:maven/org.bouncycastle/bcutil-jdk18on",
          "packageName": "bcutil",
          "programFiles": [
            "AuthenticatedData"
          ],
          "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": [
            "CMSAuthenticatedDataParser"
          ],
          "collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java-lts/",
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://github.com/bcgit/bc-lts-java",
          "vendor": "Legion of the Bouncy Castle Inc.",
          "modules": [
            "util"
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          "product": "BC-LTS-JAVA",
          "versions": [
            {
              "status": "affected",
              "version": "2.73.0",
              "lessThan": "2.73.13",
              "versionType": "maven"
            }
          ],
          "platforms": [
            "all"
          ],
          "packageURL": "pkg:maven/org.bouncycastle/bcutil-lts8on",
          "packageName": "bcutil-lts8on",
          "programFiles": [
            "AuthenticatedData"
          ],
          "collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java-lts/",
          "defaultStatus": "unaffected"
        },
        {
          "vendor": "Legion of the Bouncy Castle Inc.",
          "product": "BC-FJA",
          "versions": [
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              "status": "affected",
              "version": "1.0.0",
              "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"
        },
        {
          "vendor": "Legion of the Bouncy Castle Inc.",
          "product": "BC-FJA",
          "versions": [
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              "version": "2.0.0",
              "lessThan": "2.0.8",
              "versionType": "maven"
            },
            {
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              "version": "2.1.0",
              "lessThan": "2.1.8",
              "versionType": "maven"
            }
          ],
          "platforms": [
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          ],
          "packageURL": "pkg:maven/org.bouncycastle/bcutil-fips",
          "packageName": "bcutil-fips",
          "collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java-fips/",
          "defaultStatus": "unaffected"
        }
      ]
    }
  ],
  "published": "2026-10-03T09:17:05.250",
  "references": [
    {
      "url": "https://github.com/bcgit/bc-java/commit/dcb683b32b440f1beb1d2276a34930164281fb95",
      "source": "91579145-5d7b-4cc5-b925-a0262ff19630"
    },
    {
      "url": "https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9071888",
      "source": "91579145-5d7b-4cc5-b925-a0262ff19630"
    }
  ],
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "91579145-5d7b-4cc5-b925-a0262ff19630",
      "description": [
        {
          "lang": "en",
          "value": "CWE-354"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "In Bouncy Castle for Java before 1.86, the streaming CMS AuthenticatedData parser accepted a message whose digestAlgorithm and authAttrs fields disagreed about whether authenticated attributes were present. RFC 5652 sec. 9.1 pairs the two, requiring that authAttrs be present whenever digestAlgorithm is, and sec. 9.2 makes the MAC cover the DER encoding of authAttrs when they are present and the eContent OCTET STRING directly when they are not. CMSAuthenticatedDataParser has to choose between those two in its constructor, before it can reach authAttrs, which comes later in the SEQUENCE, so it chose on digestAlgorithm alone: for a message with digestAlgorithm absent but authAttrs present it verified the content MAC and then returned the attributes through getAuthAttrs() as though they had been authenticated, when the MAC had never covered them. An attacker able to modify a message in transit could insert an authenticated attribute, such as an RFC 2634 ESSSecurityLabel, into an otherwise valid message while holding neither the key-encryption key nor the content-MAC key, and an application taking an authorization, routing or labelling decision from those attributes would act on attacker-chosen values. The content itself remained MAC-bound. asn1.cms.AuthenticatedData now rejects the mismatched pairing when parsing and CMSAuthenticatedDataParser cross-checks the two fields once authAttrs is read. This is a variant of CVE-2026-59642, which bound the content to the MAC for messages that legitimately carry authAttrs, and which does not address this case. This issue also affects Bouncy Castle for Java LTS before 2.73.13, and 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), and bcutil-fips 2.0.8 (2.0.X series) and 2.1.8 (2.1.X series)."
    }
  ],
  "lastModified": "2026-10-06T14:49:40.823",
  "sourceIdentifier": "91579145-5d7b-4cc5-b925-a0262ff19630"
}