Microsoft Outlook Improper Input Validation Vulnerability
What it is
Microsoft Outlook contains an improper input validation vulnerability that allows for remote code execution. Successful exploitation of this vulnerability would allow an attacker to bypass the Office Protected View and open in editing mode rather than protected mode.
Who's affected
Affects anyone using Microsoft 365 or Office to compose, store, or send email, documents, or spreadsheets. In a small practice, that's typically where client communications, engagement letters, and case notes live — credential compromise here means an attacker reads everything that platform stores.
What to do
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
CISA action deadline: February 27, 2025. Federal agencies must complete the required action by this date. For private SMBs the deadline is advisory — but treat it as a strong recommendation, especially if you handle regulated data (HIPAA, GLBA, ABA model rules).
If you don't have someone in-house to verify the patch deployed across every endpoint — or you're not sure whether you're affected — that's exactly the kind of triage we do. Book a free 20-minute triage call.
Severity
CVSS base score: 9.8 — CRITICAL
Weakness classification: CWE-20
Source
Pulled daily from the public cisagov/kev-data mirror (CC0). View the original entry on cisa.gov. CISA KEV is US-Government public-domain data; we add the SMB-vertical framing and the coping action above.