Microsoft Outlook Security Feature Bypass Vulnerability

What it is

Microsoft Outlook contains a security feature bypass vulnerability that allows an attacker to bypass the Microsoft Outlook Security Notice prompt.

Who's affected

Affects anyone using Outlook as their mail client. In a CPA or legal practice, Outlook is typically how staff send privileged correspondence and exchange documents — credential or session compromise here exposes that.

What to do

Apply updates per vendor instructions or discontinue use of the product if updates are unavailable.

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.

Microsoft fix

• Click to Run (Security Update)
• KB5002427 (Security Update)
• KB5002432 (Security Update)

Sourced from Microsoft Security Update Guide (CVRF document 2023-Jul).

CISA due date

Federal deadline: August 1, 2023. 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).

EPSS

EPSS score: 15.5% — higher than 97% of all scored CVEs.

EPSS estimates the probability of exploitation activity in the next 30 days. Every entry on this site is already confirmed exploited, so read it as relative urgency among the things you still have open, not as permission to wait.

Score dated 2026-08-12, from the FIRST.org Exploit Prediction Scoring System.

Browse more

• All Microsoft KEV entries
• All SMB-relevant KEV entries

Source

This entry comes from CISA's Known Exploited Vulnerabilities catalog, public US-Government data we pull daily. The plain-language framing and the what-to-do guidance above are ours. View the original entry on cisa.gov.