The vulnerability arises when wolfSSL’s X.509 validation logic does not correctly enforce NameConstraints extensions in certificate chains that include an unconstrained intermediate CA. The flaw causes the library to reset its validation state and accept leaf certificates for hostnames that should be disallowed, effectively bypassing cryptographic delegation controls and allowing an attacker to spoof legitimate hostnames.

wolfSSL, versions 5.9.2 and earlier. The issue appears in the default build configuration when NameConstraints extensions are used in the certificate chain.

The CVSS score of 6.3 indicates a moderate severity. EPSS data is unavailable, and the vulnerability is not listed in CISA’s KEV catalog. The attack requires constructing a certificate chain that contains a name‑constrained intermediate CA followed by an unconstrained CA tier before the leaf certificate. An adversary could then use the wolfSSL library to validate this chain and obtain a seemingly legitimate certificate for a rejected hostname. The exploit is feasible but limited by the need to supply a specific chain, so the overall risk is moderate.