Legion of the Bouncy Castle BC-JAVA/BC-LTS-JAVA/BC-FJA prior 1.86/2.73.13/1.0.13/2.0.13/2.1.13 Certificate Path Reviewer PKIXCertPathReviewer.java isValidCertPath certificate validation

Summaryinfo

A vulnerability, which was classified as problematic, was found in Legion of the Bouncy Castle BC-JAVA, BC-LTS-JAVA and BC-FJA. This affects the function isValidCertPath of the file org/bouncycastle/pkix/jcajce/PKIXCertPathReviewer.java of the component Certificate Path Reviewer. Executing a manipulation can lead to certificate validation. This vulnerability appears as CVE-2026-71889. The attack may be performed from remote. There is no available exploit. You should upgrade the affected component.

Detailsinfo

A vulnerability has been found in Legion of the Bouncy Castle BC-JAVA, BC-LTS-JAVA and BC-FJA and classified as problematic. This vulnerability affects the function isValidCertPath of the file org/bouncycastle/pkix/jcajce/PKIXCertPathReviewer.java of the component Certificate Path Reviewer. The manipulation with an unknown input leads to a certificate validation vulnerability. The CWE definition for the vulnerability is CWE-295. The product does not validate, or incorrectly validates, a certificate. As an impact it is known to affect integrity. CVE summarizes:

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).

The advisory is available at github.com. This vulnerability was named CVE-2026-71889 since 08/08/2026. The exploitation appears to be difficult. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1587.003 by the MITRE ATT&CK project.

Upgrading to version 1.86, 2.73.13, 1.0.13, 2.0.13 or 2.1.13 eliminates this vulnerability.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Type

• Programming Language Software

Vendor

• Legion of the Bouncy Castle

Name

• BC-FJA
• BC-JAVA
• BC-LTS-JAVA

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Discussion