CVE-2026-21509
HIGHCVSS Vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Lifecycle Timeline
4Description
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
Analysis
Microsoft Office contains a security feature bypass (CVE-2026-21509, CVSS 7.8) where reliance on untrusted inputs in security decisions allows local attackers to bypass protections designed to prevent execution of malicious content. KEV-listed with EPSS 9.3%, this vulnerability enables attackers to circumvent Office security features like Protected View or macro restrictions through crafted documents.
Sign in for full analysis, threat intelligence, and remediation guidance.
Remediation
Within 24 hours: Assess inventory of Microsoft Office deployments and identify business-critical systems; communicate vulnerability to all stakeholders and restrict Office file sharing from untrusted sources. Within 7 days: Implement compensating controls listed below; enhance monitoring for suspicious Office file activity and privilege escalation attempts; conduct threat hunting for indicators of compromise. …
Sign in for detailed remediation steps.
Priority Score
Share
External POC / Exploit Code
Leaving vuln.today