High 8.7Published Oct 3, 2026

CVE-2026-71889PKIXCertPathReviewer does not apply X.509 name constraints to the target certificate

Updated under an hour ago (2026-10-19 06:10 UTC)

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It affects Legion of the Bouncy Castle Inc. BC-JAVA and 2 other products. Add what you run to find out whether that includes you.

EPSS puts the chance of exploitation in the next 30 days at 0.17%, higher than 6% of scored CVEs.

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Every CVE for Legion of the Bouncy Castle Inc. BC-JAVA

Exploited in the last 30 days

In Bouncy Castle for Java before 1.86, neither copy of PKIXCertPathReviewer - org.bouncycastle.pkix.jcajce.PKIXCertPathReviewer nor the legacy org.bouncycastle.x509.PKIXCertPathReviewer - applied X.509 name constraints to the end-entity certificate. checkNameConstraints walked the path with a loop bound of index greater than zero, which is the bound the CA-only steps require, but index zero is the target certificate under the standard CertPath ordering, so the permitted and excluded subtree checks of RFC 5280 sec. 6.1.3 (b) and (c) never ran against the leaf's subject DN or its subjectAltName. A chain whose leaf violated a NameConstraints extension imposed by its own issuing CA therefore reported isValidCertPath() true with an empty error list, while CertPathValidator.getInstance("PKIX", "BC"), which shares no code with the reviewer, rejected the identical chain against the identical trust anchor. An application using the reviewer to make the trust decision rather than for diagnostics alongside a real validation accepted a certificate the constrained CA was never authorised to issue. Both copies now check every certificate in the path including the target, waive the sec. 4.2.1.10 self-issued exemption for the final certificate as sec. 6.1.3 requires, and skip the sec. 6.1.4 (g) constraint-accumulation step for the target. This issue also affects Bouncy Castle for Java LTS before 2.73.13, which carries only the org.bouncycastle.pkix.jcajce copy of the reviewer. It also affects 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).

CVSS: 8.7 HIGH (v4.0, CNA)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/U:Amber
Weakness (CWE): CWE-295
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): 0.17% (percentile 6)
Assigned by: bcorg
NVD analysis: Awaiting Analysis
Record last updated: Oct 5, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Legion of the Bouncy Castle Inc. BC-JAVA legion_of_the_bouncy_castle:bc_java (from the name)	before 1.86	CNA record
Legion of the Bouncy Castle Inc. BC-LTS-JAVA legion_of_the_bouncy_castle:bc_lts_java (from the name)	from 2.73.0 before 2.73.13	CNA record
Legion of the Bouncy Castle Inc. BC-FJA legion_of_the_bouncy_castle:bc_fja (from the name)	from 1.0.4 before 1.0.13; from 2.0.0 before 2.0.13; from 2.1.0 before 2.1.13	CNA record

References

https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9071889vendor-advisory
https://github.com/bcgit/bc-java/commit/06dcff2f51037095de126986285c998e3455ab85patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.