CVE-2026-71889 (GCVE-0-2026-71889)

Vulnerability from cvelistv5 – Published: 2026-10-03 08:31 – Updated: 2026-10-03 08:31
VLAI
Title
PKIXCertPathReviewer does not apply X.509 name constraints to the target certificate
Summary
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).
Severity
8.7 (High)
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
CWE
  • CWE-295 - Improper Certificate Validation
Assigner
References
Impacted products
Vendor Product Version
Legion of the Bouncy Castle Inc. BC-JAVA Affected: 0 , < 1.86 (maven)
Create a notification for this product.
Legion of the Bouncy Castle Inc. BC-LTS-JAVA Affected: 2.73.0 , < 2.73.13 (maven)
Create a notification for this product.
Legion of the Bouncy Castle Inc. BC-FJA Affected: 1.0.4 , < 1.0.13 (maven)
Affected: 2.0.0 , < 2.0.13 (maven)
Affected: 2.1.0 , < 2.1.13 (maven)
Create a notification for this product.
Credits
Yu Bao from the PayPal Cyber Security Team
Show details on NVD website
To clipboard 

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          "type": "reporter",
          "value": "Yu Bao from the PayPal Cyber Security Team"
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            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
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            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
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            "exploitMaturity": "NOT_DEFINED",
            "privilegesRequired": "NONE",
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            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
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            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE",
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          "url": "https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9071889"
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          "url": "https://github.com/bcgit/bc-java/commit/06dcff2f51037095de126986285c998e3455ab85"
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      "x_generator": {
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    "dateReserved": "2026-08-08T00:06:07.401Z",
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