CVE-2025-46421 and is rated Medium severity with a CVSS score of 6.8. 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 12, 2026
CBL-Mariner Releases
Vendor-listed releases
3.0.4-5
3.4.4-5
CISA KEVNot listedBased on the latest collected catalog
EPSS0.6%Estimated 30-day exploitation probability
Ransomware useNot markedCISA KEV ransomware field
Threat actors0Source-linked actor relationships
Overview
What is CVE-2025-46421?
A flaw was found in libsoup. When libsoup clients encounter an HTTP redirect, they mistakenly send the HTTP Authorization header to the new host that the redirection points to.
This allows the new host to impersonate the user to the original host that issued the redirect.