Known exploited · Microsoft
CVE-2024-21413: 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.
- Vendor
- Microsoft
- Product
- Office Outlook
- Added to KEV
- February 6, 2025
- CISA due date
- February 27, 2025
- Ransomware use
- Unknown
What CISA requires
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
Forensic triage
No
What to do now
- Find every instance of Office Outlook you run, including the forgotten ones, and check its version against the vendor advisory.
- Apply the vendor's fix or mitigation, before February 27, 2025 if you are bound by CISA's deadline, sooner if it faces the internet.
- Assume it was tried against you already: look for signs of exploitation from the date it was added, not from the day you patched.
References
H2 Security
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Start freeSource: CISA Known Exploited Vulnerabilities Catalog (public domain), catalog version 2026.10.01.