CVE-2026-71886

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Source

https://cve.org/CVERecord?id=CVE-2026-71886

Import Source

https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-71886.json

JSON Data

https://api.test.osv.dev/v1/vulns/CVE-2026-71886

Downstream

Related

Published

2026-10-03T08:46:33Z

Modified

2026-10-22T16:39:14Z

Severity

8.2 (High) CVSS_V4 - 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/U:Amber CVSS Calculator

Summary

OpenPGP certification accepted from a subkey without certification authority

Details

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 subkey to the primary key's identity-issuing authority, defeating the containment the key-flag separation provides. A third-party certification or delegation is now attributed to the issuing certificate only when the component key that made it is the primary key, or is a subkey holding CERTIFY_OTHER when the signature was created, so certification-capable subkeys continue to be accepted; primary keys are accepted whatever their key flags say, since a primary key is certification-capable by construction and certificates carrying no key flags subpacket at all are common. Third-party revocations are deliberately outside the rule, since declining to honour one would keep trust alive rather than withdraw it.

Database specific

{
    "cna_assigner": "bcorg",
    "cwe_ids": [
        "CWE-285",
        "CWE-863"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/71xxx/CVE-2026-71886.json"
}

References

Affected packages

Git / github.com/bcgit/bc-java

Affected ranges

Type

GIT

Repo

https://github.com/bcgit/bc-java

Events

Introduced

228211ecb973fe87fdd0fc4ab16ba0446ec1a29c

Fixed

eacda831fbe15b272933e40841d8b0827b556fae

Fixed

f0d5c8535aeff3f34b7b6b6289ee78c2ea36a3fb

Database specific

Show details

{
    "extracted_events": [
        {
            "range": [
                {
                    "introduced": "1.81"
                },
                {
                    "fixed": "1.86"
                }
            ],
            "source": "AFFECTED_FIELD",
            "strategy": "StandardRange"
        },
        {
            "range": [
                {
                    "fixed": "f0d5c8535aeff3f34b7b6b6289ee78c2ea36a3fb"
                }
            ],
            "source": "REFERENCES_COMMIT"
        }
    ]
}

Database specific

source

"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-71886.json"

vanir_signatures

[
    {
        "deprecated": false,
        "digest": {
            "function_hash": "92728918085483818624135828885250796945",
            "length": 654
        },
        "id": "CVE-2026-71886-719a36c6",
        "signature_type": "Function",
        "signature_version": "v1",
        "source": "https://github.com/bcgit/bc-java/commit/f0d5c8535aeff3f34b7b6b6289ee78c2ea36a3fb",
        "target": {
            "file": "pg/src/main/java/org/bouncycastle/openpgp/api/OpenPGPCertificate.java",
            "function": "getMergedDanglingExternalSignatureChainEndsFrom"
        }
    },
    {
        "deprecated": false,
        "digest": {
            "line_hashes": [
                "96044263478928036066923524062525021264",
                "242487062344332550567517235893918196467",
                "152891498374372822831571267334452984753",
                "333006426170499316169006874622780740915"
            ],
            "threshold": 0.9
        },
        "id": "CVE-2026-71886-805740fb",
        "signature_type": "Line",
        "signature_version": "v1",
        "source": "https://github.com/bcgit/bc-java/commit/f0d5c8535aeff3f34b7b6b6289ee78c2ea36a3fb",
        "target": {
            "file": "pg/src/test/java/org/bouncycastle/openpgp/api/test/RegressionTest.java"
        }
    },
    {
        "deprecated": false,
        "digest": {
            "line_hashes": [
                "90602617907301426648126531739415962309",
                "57142368514420324495394381481274598647",
                "198483668386199754599530411782955208446",
                "201586600117416069860992628273320755579",
                "144638274316590469724206700312500581269",
                "283782780981136109616440998703198800326",
                "233536536377518901883844857438464715310",
                "55105660343254344232119973270498110244"
            ],
            "threshold": 0.9
        },
        "id": "CVE-2026-71886-a840a4ea",
        "signature_type": "Line",
        "signature_version": "v1",
        "source": "https://github.com/bcgit/bc-java/commit/f0d5c8535aeff3f34b7b6b6289ee78c2ea36a3fb",
        "target": {
            "file": "pg/src/main/java/org/bouncycastle/openpgp/api/OpenPGPCertificate.java"
        }
    }
]

vanir_signatures_modified

"2026-10-22T16:39:14Z"