# CVE-2026-71886: OpenPGP certification accepted from a subkey without certification authority > Attackers can exploit compromised subkeys to forge OpenPGP certifications, bypassing key flag restrictions and falsely attributing identity assertions to the primary key. - **Severity:** High 8.2 (`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`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 3 Oct 2026 - **Updated:** 5 Oct 2026 - **Also known as:** CLEANSTART-2026-WJ50656, DEBIAN-CVE-2026-71886, GHSA-7hrr-mw36-px4x, UBUNTU-CVE-2026-71886 ## What is CVE-2026-71886? CVE-2026-71886 is a high-severity authentication bypass vulnerability in Legion of the Bouncy Castle Inc. BC-JAVA, published on 3 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description 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. Weakness: CWE-863 (Incorrect Authorization), CWE-285 (Improper Authorization) ## Which versions are affected by CVE-2026-71886? ## How do I fix CVE-2026-71886? Upgrade to a fixed version. ## Is CVE-2026-71886 being exploited? There is no known exploitation of CVE-2026-71886 in the wild and no public exploit code. ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-71886 and fix it if it is affected. What it is: CVE-2026-71886 is a high-severity authentication bypass vulnerability in Legion of the Bouncy Castle Inc. BC-JAVA, published on 3 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2026-71886 in the wild and no public exploit code. Affected product: Legion of the Bouncy Castle Inc. BC-JAVA. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-71886/ (Markdown: https://insights.sbomify.com/CVE-2026-71886/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-71886 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-71886 - OSV: https://osv.dev/vulnerability/CVE-2026-71886 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-71886/ Summaries are generated and may contain mistakes; the official description above is the record.