bouncycastle — security advisory

{
  "id": "781fc163409e715cb5869c508dee09a9dd00d1455913b3527b23233b6d6e66ba",
  "url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-71886",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "DEBIAN-CVE-2026-71886",
    "summary": "In Bouncy Castle for Java before 1.86, the high-level OpenPGP certificate API accepted a third-party certification or trust delegation from any component key of the issuing certificate, without requiring that component to have been granted the authority to certify. OpenPGPCertificate.getCertificationBy() and getDelegationBy() resolve a third-party signature by matching its issuer key identifier against every key of the third-party certificate, then verify the issuing component's binding chain and the signature itself; nothing checked that the issuing component carried the RFC 9580 sec. 5.2.3.29 certification key flag (CERTIFY_OTHER) when the signature was created. A subkey bound only with SIGN_DATA - the online signing subkey of exactly the offline-primary arrangement those key flags exist to express - could therefore issue a positive User ID certification over an attacker-controlled identity, or a full-trust depth-one direct-key delegation of introducer trust, and the API returned it as a valid signature chain attributed to the third-party certificate. An application treating getCertificationBy(...).isValid() or getDelegationBy(...) as an identity or trusted-introducer decision would attribute the attacker's assertion to the offline primary key. The same held for a legacy RSA subkey bound only for encryption, whose algorithm is nonetheless able to sign. This does not forge the primary key's signature or recover any private key; it promotes an already-compromised restricted s",
    "evidence": "osv:DEBIAN-CVE-2026-71886",
    "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": "high",
    "structured": {
      "id": "DEBIAN-CVE-2026-71886",
      "aliases": [
        "DEBIAN-CVE-2026-71886"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/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"
        }
      ],
      "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-2026-71886.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-2026-71886.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-2026-71886.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        }
      ],
      "modified": "2026-10-07T09:47:34.259863466Z",
      "provider": "osv",
      "upstream": [
        "CVE-2026-71886"
      ],
      "references": [
        "https://security-tracker.debian.org/tracker/CVE-2026-71886"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2026-71886",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 94663,
  "published_at": "2026-10-03T09:17:04.897+00:00"
}