Microsoft Outlook Remote Code Execution Vulnerability

cisa required action Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

1. 2024-02-13 Published
2. 2025-02-06 Added to CISA KEV
3. 2025-02-07 CISA SSVC: exploitation active
4. 2025-02-27 CISA patch deadline

Added

21 mo ago (2025-02-06)

Patch by

2025-02-27 (20 mo ago)

Ransomware

Not known

Required action

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

Vendor, product

Microsoft, Office Outlook

CISA name

Microsoft Outlook Improper Input Validation Vulnerability

How it is exploited and what it leads to, in MITRE ATT&CK terms.

• T1566.002 Spearphishing Link exploitation
• T1059 Command and Scripting Interpreter primary impact

kev release 2025-07-28, att&ck v16.1. KEV to ATT&CK mappings by the MITRE Center for Threat-Informed Defense (Mappings Explorer, Apache-2.0). © 2026 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation. Terms of use

Exploitation

Active, exploited in the wild

Automatable

yes

Technical impact

total

Assessed

21 mo ago (2025-02-07)

94.66% chance of exploitation in the next 30 days, higher than 99.8% of all scored CVEs (FIRST EPSS, 2026-11-08).

• vicarius.io https://www.vicarius.io/vsociety/posts/cve-2024-21413-critical-monikerlink-vulnerability-affecting-microsoft-outlook-detection-script referenced PoC, tagged "exploit" by a source, unverified

• Microsoft Microsoft 365 Apps for Enterprise
• Microsoft Microsoft Office 2016
• Microsoft Microsoft Office 2019
• Microsoft Microsoft Office LTSC 2021

Weakness

• CWE-20 Improper Input Validation

• msrc.microsoft.com /update-guide/vulnerability/CVE-2024-21413

  vendor-advisory, patch

• vicarius.io /vsociety/posts/cve-2024-21413-critical-monikerlink-vulnerability-affecting-microsoft-outlook-detection-script

  exploit

• cisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-21413

  government-resource, us-government-resource

• vicarius.io /vsociety/posts/cve-2024-21413-critical-monikerlink-vulnerability-affecting-microsoft-outlook-mitigation-scrip

  mitigation

• research.checkpoint.com /2024/the-risks-of-the-monikerlink-bug-in-microsoft-outlook-and-the-big-picture/

  technical-description

• CVE List CVE-2024-21413
• NVD CVE-2024-21413

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.