CVE-2026-121031 and is rated Medium severity with a CVSS score of 6.5. 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: Nov 5, 2026
Release Notes
Vendor-listed releases
157.0.4341.42
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-2026-121031?
Missing authorization in PDF in Google Chrome prior to 157.0.8103.38 allowed a remote attacker to bypass web origin policy into a privileged page via a crafted Chrome extension. (Chromium security severity: Medium)