Widespread use of gnutls TLS stack; cert validation bypass enables MITM across many services.
CVE-2026-42013
TLS cert validation bypass in gnutls via oversized SAN enabling MITM.
Is CVE-2026-42013 being exploited?
Not confirmed. CVE-2026-42013 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.42% probability of exploitation in the next 30 days.
How severe is CVE-2026-42013?
CVE-2026-42013 is rated High with a CVSS score of 8.2. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-42013?
Yes. A fix has been recorded for CVE-2026-42013. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-42013 affect?
CVE-2026-42013 affects gnutls library, TLS-enabled apps using gnutls. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-42013?
Update to patched gnutls version immediately
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Attacker can bypass certificate validation, enabling remote MITM and spoofing on TLS connections.
Immediate action required