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Exploited

CVE-2024-21413

Microsoft Outlook · Email

Microsoft Outlook Improper Input Validation Vulnerability

What should I do? View at Microsoft

At a glance

Exploited. Added to CISA’s catalog of exploited vulnerabilities on February 6, 2025.

Affected product: Microsoft Outlook (category Email, indicative classification). Name in CISA’s catalog: Microsoft Office Outlook.

Microsoft component: Outlook (Messaging and collaboration).

What should I do?

Apply the patches or mitigations from Microsoft; if none are available, stop using the product.

Deadline set by CISA for US federal agencies: 21 days (due February 27, 2025). It only binds those agencies, but it is a useful measure of urgency.

Original text of the required action (CISA)

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

Timeline

  1. Vulnerability published Publication date (NVD)
  2. Exploitation confirmed Added to CISA’s KEV catalog
  3. CISA deadline Remediation deadline set for US federal agencies

The facts, with their sources

Exploitation confirmed
Yes, on February 6, 2025 Date added to the catalog of exploited vulnerabilities. Exploitation itself may have started earlier. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
Ransomware
No known use to date That does not guarantee it is not being used: the information is not public. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
Hunt for compromise
Not requested by CISA Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
CISA required action
Apply the patches or mitigations from Microsoft; if none are available, stop using the product. Rewritten by this site from CISA’s original text. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
CISA deadline
February 27, 2025, 21 days Set for US federal agencies: a measure of urgency, not an obligation elsewhere. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
Microsoft patch
Not available Source: Security Update Guide, collected September 29, 2026 at 14:57 UTC
Vulnerability published
February 13, 2024 Source: National Vulnerability Database (NVD), collected September 29, 2026 at 15:00 UTC
Product according to CISA
Microsoft Office Outlook Filed by this site under “Email” (indicative classification). Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Technical detail of the score: attack vector, complexity, impact. Source: National Vulnerability Database (NVD), collected September 29, 2026 at 15:00 UTC

Severity and activity

9.8 / 10 CVSS severity: critical

Score from the vendor or CISA, relayed by the NVD. Collected Sep 29, 2026.

— Probability of exploitation in the next 30 days (EPSS)

FIRST’s EPSS model. Since exploitation is already confirmed, this figure is mostly useful to compare activity. Collected Sep 29, 2026.

Description

Microsoft Outlook Remote Code Execution Vulnerability

Official description from the NVD, collected Sep 29, 2026. CVE® description © The MITRE Corporation.

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.

Summary from CISA (KEV catalog).

CERT-FR advisories

Information reused under the Open Licence 2.0 (Etalab); the date of last update is shown for each advisory. This site is neither affiliated with nor endorsed by ANSSI.

Sources for this page