Published May 18, 2026Sources checked Nov 11, 2026
7.5HIGHCVSS out of 10
What this means
Review the available evidence
CVE-2026-42009 and is rated High severity with a CVSS score of 7.5. 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 3, 2026
CBL-Mariner Releases
Vendor-listed releases
3.8.3-11
CISA KEVNot listedBased on the latest collected catalog
EPSS1.3%Estimated 30-day exploitation probability
Ransomware useNot markedCISA KEV ransomware field
Threat actors0Source-linked actor relationships
Overview
What is CVE-2026-42009?
A flaw was found in gnutls. A remote attacker could exploit an issue in the Datagram Transport Layer Security (DTLS) packet reordering logic.
The comparator function, responsible for ordering DTLS packets by sequence numbers, did not correctly handle packets with duplicate sequence numbers. This could lead to unstable packet ordering or undefined behavior, resulting in a denial of service.