Published Jun 29, 2025Sources checked Nov 11, 2026
7.8HIGHCVSS out of 10
What this means
Review the available evidence
CVE-2025-6856 and is rated High severity with a CVSS score of 7.8. 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: Aug 7, 2026
CBL-Mariner Releases
Vendor-listed releases
1.14.6-1
CISA KEVNot listedBased on the latest collected catalog
EPSS0.3%Estimated 30-day exploitation probability
Ransomware useNot markedCISA KEV ransomware field
Threat actors0Source-linked actor relationships
Overview
What is CVE-2025-6856?
A vulnerability, which was classified as problematic, was found in HDF5 1.14.6. Affected is the function H5FL__reg_gc_list of the file src/H5FL.c.
The manipulation leads to use after free. Attacking locally is a requirement.
The exploit has been disclosed to the public and may be used.