Published Jun 19, 2026Sources checked Oct 28, 2026
4.9MEDIUMCVSS out of 10
What this means
Review the available evidence
CVE-2026-56131 and is rated Medium severity with a CVSS score of 4.9. 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: Jul 3, 2026
CBL-Mariner Releases
Vendor-listed releases
2.8.2-1
CISA KEVNot listedBased on the latest collected catalog
EPSS0.2%Estimated 30-day exploitation probability
Ransomware useNot markedCISA KEV ransomware field
Threat actors0Source-linked actor relationships
Overview
What is CVE-2026-56131?
libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser from within handlers in cases of a policy violation. Thus, a use-after-free can occur (similar to the CVE-2026-50219 situation).