CVE-2024-21413: Microsoft Outlook Improper Input Validation Vulnerability
Affects Microsoft Office OutlookSource CISA KEV
Exploited in the wild · KEV due 27 Feb 2025 · 94% EPSS : apply the vendor's fix or mitigations to Microsoft Office Outlook now.
Data as of 10/24/2026, 22:15:59 UTC
- Exploitation
Actively exploited – in CISA KEV since 02/06/2025
- KEV deadline
- 02/27/2025 US federal agencies must patch by this date; a sensible deadline for everyone else.
- EPSS
- 94.6% chance of exploitation in 30 days – higher than 99% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:CWhat to do
CISA required action
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
Description
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.
Weaknesses
- CWE-20Improper Input Validation (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #18OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.