cve 2026 42013

The cve 2026 42013 tag covers a GnuTLS certificate-validation flaw documented in Microsoft’s Security Update Guide. The issue involves an oversized Subject Alternative Name that can cause vulnerable GnuTLS builds to fall back to the certificate’s Common Name during validation. That behavior may enable certificate spoofing or man-in-the-middle attacks in software relying on affected libraries. The coverage is relevant to Windows administrators because modern environments often include Linux systems, containers, appliances, developer tools, package mirrors, proxies, and other hybrid infrastructure. Use this tag to follow discussion of the vulnerability, its TLS validation implications, and the risks it creates across mixed technology estates.