Executive brief
wolfSSL is a security library used by many devices and applications to establish secure connections. A flaw was found where the library failed to properly check certain security restrictions (name constraints) on digital certificates that use wildcards (like *.example.com). This could allow a malicious or compromised certificate authority to issue certificates for websites they aren't authorized to represent, potentially allowing them to impersonate legitimate services.
Technical details
A vulnerability in wolfSSL's certificate validation logic allows certificates with wildcard DNS Subject Alternative Names (SANs) to bypass Name Constraint checks. Specifically, the library failed to correctly apply permitted or excluded DNS name constraints defined by an issuing CA when the leaf certificate utilized a wildcard (e.g., *.example.com). This improper validation (CWE-295) could allow a constrained intermediate CA to issue unauthorized certificates that would be accepted as valid by the library. The issue was addressed by implementing RFC 5280-compliant nameConstraint handling for wildcard DNS SANs and normalizing trailing-dot DNS names. The fix is available in wolfSSL version 5.9.1.
Affected products
- wolfSSL wolfSSL 3.9.10 through 5.9.1
Timeline
- 2026-05-28: other: Pull request submitted to wolfSSL repository
- 2026-06-04: patched: Fix merged into master branch
- 2026-06-25: disclosed: CVE published to NVD