Published May 26, 2026Sources checked Nov 11, 2026
8.2HIGHCVSS out of 10
What this means
Review the available evidence
CVE-2026-42013 and is rated High severity with a CVSS score of 8.2. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.
What to do next
Remediation and response
Microsoft Security Response Center guidance
Vendor revision: Jun 11, 2026
CBL-Mariner Releases
Vendor-listed releases
3.8.13-1
CISA KEVNot listedBased on the latest collected catalog
EPSS0.4%Estimated 30-day exploitation probability
Ransomware useNot markedCISA KEV ransomware field
Threat actors0Source-linked actor relationships
Overview
What is CVE-2026-42013?
A flaw was found in gnutls. When validating certificates, an oversized Subject Alternative Name (SAN) could cause the validation process to incorrectly fall back to checking the Common Name (CN) field.
This could allow a remote attacker to bypass proper certificate validation, potentially leading to spoofing or man-in-the-middle attacks.