Published Mar 20, 2026Sources checked Nov 11, 2026
3.3LOWCVSS out of 10
What this means
Review the available evidence
CVE-2026-4519 and is rated Low severity with a CVSS score of 3.3. 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: Oct 28, 2026
CBL-Mariner Releases
Vendor-listed releases
3.12.9-10
3.9.19-20
Microsoft Security Response Center guidance
Vendor revision: Aug 10, 2026
CBL-Mariner Releases
Vendor-listed releases
3.12.9-14
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-2026-4519?
The webbrowser.open() API would accept leading dashes in the URL which could be handled as command line options for certain web browsers. New behavior rejects leading dashes.
Users are recommended to sanitize URLs prior to passing to webbrowser.open().