CVE-2026-89133
Received Received - Intake

wolfSSL X.509 NameConstraints Validation Bypass

Publication date: 2026-09-27

Last updated on: 2026-09-27

Assigner: wolfSSL Inc.

Description
wolfSSL versions 5.9.2 and earlier contain a flaw in the X.509 certificate validation logic where it fails to properly enforce NameConstraints extensions when there is an unconstrained CA tier between a name-constrained intermediate CA and the leaf certificate. wolfSSL incorrectly accepted certificates for hostnames they shouldn't be allowed to cover, due to a chain-walking state-machine bug that resets the validation state when encountering an intermediate without NameConstraints, thereby bypassing cryptographic delegation controls. This defect exists in the default build configuration that makes use of certificates where name constraint extensions are used. Thanks to Jack Lloyd, PathDiff, and Ben Smyth for reporting the issue.

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Meta Information

Published
2026-09-27
Last Modified
2026-09-27
Generated
2026-09-27
AI Q&A
2026-09-27
EPSS Evaluated
N/A
NVD
CVE-2026-89133
EUVD
EUVD-2026-87922

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
wolfssl wolfssl to 5.9.2 (exc)

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-295 The product does not validate, or incorrectly validates, a certificate.

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Executive Summary

wolfSSL versions 5.9.2 and earlier have a flaw in X.509 certificate validation where NameConstraints extensions are not properly enforced. When an unconstrained CA exists between a name-constrained intermediate CA and a leaf certificate, wolfSSL incorrectly accepts certificates for unauthorized hostnames due to a chain-walking bug that resets validation state upon encountering an intermediate without NameConstraints.

Detection Guidance

To detect this vulnerability, inspect wolfSSL certificate chains for improper NameConstraints enforcement. Check if intermediate CAs without NameConstraints reset validation state. Use wolfSSL's test suites like test_wolfSSL_CertManagerNameConstraint_valid_chain to verify correct behavior. Examine logs for certificate validation failures or unexpected hostname matches.

Impact Analysis

This vulnerability allows attackers to bypass cryptographic delegation controls, potentially enabling unauthorized certificate issuance for hostnames that should be restricted. This could lead to man-in-the-middle attacks or impersonation of trusted services if exploited.

Compliance Impact

This vulnerability could undermine compliance with standards requiring strict certificate validation, such as GDPR's data protection measures or HIPAA's secure communication requirements. By allowing improperly constrained certificates to be accepted, it risks unauthorized access or data exposure, violating trust and security controls mandated by these regulations.

Mitigation Strategies

Upgrade wolfSSL to a version that includes the fix from pull request #10687. Disable NameConstraints if not required. Review certificate chains to ensure proper NameConstraints enforcement. Monitor for unauthorized certificate issuance or hostname mismatches.

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