CVE-2026-71889

Name of the Vulnerable Software and Affected Versions Bouncy Castle for Java versions prior to 1.86 Bouncy Castle for Java LTS versions prior to 2.73.13 Bouncy Castle for Java FIPS (BC-FJA) bcpkix-fips versions prior to 1.0.13 Bouncy Castle for Java FIPS (BC-FJA) bcpkix-fips versions prior to 2.0.13 Bouncy Castle for Java FIPS (BC-FJA) bcpkix-fips versions prior to 2.1.13

Description Both org.bouncycastle.pkix.jcajce.PKIXCertPathReviewer and the legacy org.bouncycastle.x509.PKIXCertPathReviewer fail to apply X.509 name constraints to the end-entity certificate. This occurs because the checkNameConstraints() function processes the certificate path using a loop bound that excludes index zero, which represents the target certificate. Consequently, permitted and excluded subtree checks are not performed against the leaf certificate's subject DN or its subjectAltName. This allows a certificate chain to be validated as true even if the leaf violates name constraints imposed by its issuing CA, potentially leading an application to accept a certificate that the CA was not authorized to issue.

Recommendations Update Bouncy Castle for Java to version 1.86 or later. Update Bouncy Castle for Java LTS to version 2.73.13 or later. Update Bouncy Castle for Java FIPS (BC-FJA) bcpkix-fips 1.0.X series to version 1.0.13 or later. Update Bouncy Castle for Java FIPS (BC-FJA) bcpkix-fips 2.0.X series to version 2.0.13 or later. Update Bouncy Castle for Java FIPS (BC-FJA) bcpkix-fips 2.1.X series to version 2.1.13 or later.