CVE-2025-61727

A flaw was found in the crypto/x509 package in the Go standard library. This vulnerability allows a certificate validation bypass via an excluded subdomain constraint in a certificated chain as it does not restrict the usage of wildcard SANs in the leaf certificate.

To exploit this issue, an attacker needs to obtain a leaf certificate with a wildcard SAN (e.g., *.example.com) and the legitimate certificate policy must contain an excluded DNS name constraint (e.g., to prevent issuance for test.example.com), allowing an application using the crypto/x509 package to validate the certificate when it should have been rejected and to be vulnerable to MITM (man-in-the-middle) attacks. Additionally, the attacker does not have full control of what data can be read of modified during the attack. Due to these reasons, this flaw has been rated with a moderate severity.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.