bouncycastle — security advisory

{
  "id": "3bbb43f3f5300a19fdaccdca45401cad03bf1fde711c216fa8be4aec4f7b65ff",
  "url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-71892",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "DEBIAN-CVE-2026-71892",
    "summary": "In Bouncy Castle for Java before 1.86, the opt-in key-size validation on CMS key-transport recipients, org.bouncycastle.cms.jcajce.JceKeyTransRecipient.setKeySizeValidation(true), never ran for a message using RFC 9709 content-encryption key derivation (id-alg-cek-hkdf-sha256). The branch that should have selected the actual content-encryption algorithm carried in the key derivation AlgorithmIdentifier's parameters compared the encrypted-key byte array against the id-alg-cek-hkdf-sha256 object identifier, a comparison between a byte array and an ASN1ObjectIdentifier that is false for every possible input, so the check fell through to a key-size lookup on the outer wrapper OID. That OID identifies a key-derivation construction rather than a cipher and has no registered key size, so the size comparison was skipped entirely. A key-transport EnvelopedData or AuthEnvelopedData whose transported, HKDF-derived content-encryption key did not match the key size of the advertised content-encryption algorithm was therefore accepted even with validation explicitly enabled, silently defeating the only mechanism the API offers for enforcing recovered key size. The recipient now dispatches on the content-encryption AlgorithmIdentifier's algorithm OID, so validation checks the recovered key against the inner content-encryption algorithm. Messages with a matching key size, non-HKDF messages, and recipients that do not enable validation are unaffected. This issue also affects Bouncy Castle for",
    "evidence": "osv:DEBIAN-CVE-2026-71892",
    "products": [
      {
        "name": {
          "value": "bouncycastle",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "1.72-2",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "1.77-1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "1.80-1",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "1.80-2",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "1.80-3",
            "evidence": "/affected/0/versions"
          },
          {
            "value": "1.86-1",
            "evidence": "/affected/0/versions"
          }
        ]
      },
      {
        "name": {
          "value": "bouncycastle",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "1.80-3",
            "evidence": "/affected/1/versions"
          },
          {
            "value": "1.86-1",
            "evidence": "/affected/1/versions"
          }
        ]
      },
      {
        "name": {
          "value": "bouncycastle",
          "evidence": "/affected/2/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "1.86-1",
            "evidence": "/affected/2/ranges"
          }
        ],
        "affected_versions": [
          {
            "value": "1.80-3",
            "evidence": "/affected/2/versions"
          }
        ]
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "DEBIAN-CVE-2026-71892",
      "aliases": [
        "DEBIAN-CVE-2026-71892"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/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"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "bouncycastle",
            "purl": "pkg:deb/debian/bouncycastle?arch=source&distro=bookworm",
            "ecosystem": "Debian:12"
          },
          "versions": [
            "1.72-2",
            "1.77-1",
            "1.80-1",
            "1.80-2",
            "1.80-3",
            "1.86-1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-71892.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "bouncycastle",
            "purl": "pkg:deb/debian/bouncycastle?arch=source&distro=trixie",
            "ecosystem": "Debian:13"
          },
          "versions": [
            "1.80-3",
            "1.86-1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-71892.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "1.86-1"
                }
              ]
            }
          ],
          "package": {
            "name": "bouncycastle",
            "purl": "pkg:deb/debian/bouncycastle?arch=source&distro=forky",
            "ecosystem": "Debian:14"
          },
          "versions": [
            "1.80-3"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-71892.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        }
      ],
      "modified": "2026-10-07T09:47:32.018170489Z",
      "provider": "osv",
      "upstream": [
        "CVE-2026-71892"
      ],
      "references": [
        "https://security-tracker.debian.org/tracker/CVE-2026-71892"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2026-71892",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 94652,
  "published_at": "2026-10-03T09:17:05.913+00:00"
}