Security Digest · Vulnerability record · Known exploited
CVE-2024-21413: Microsoft Outlook Improper Input Validation Vulnerability
Exploited in the wild (CISA KEV). Microsoft Outlook Remote Code Execution Vulnerability
CISA KEV · added 2025-02-06 CVSS 9.8 Critical EPSS 94.7% · p99.9
Should you act?
Exploited: patch now if you run it
CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Yes, if you run Microsoft Office Outlook. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2025-02-06, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2025-02-27; treat that as the outer limit, not the target.
- EPSS 94.7%, percentile 99.9: FIRST’s model estimates a 94.7% chance of exploitation activity in the next 30 days, higher than 99.9% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
What it is
Microsoft Outlook Remote Code Execution Vulnerability
CISA’s summary
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.
Weakness type: CWE-20.
Product: Microsoft Office Outlook · Assigned by: microsoft · Published: 2024-02-13
Affected and fixed versions
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| Microsoft | Microsoft 365 Apps for Enterprise | 16.0.1 < https://aka.ms/OfficeSecurityReleases |
| Microsoft | Microsoft Office 2016 | 16.0.0 < 16.0.5435.1001 |
| Microsoft | Microsoft Office 2019 | 19.0.0 < https://aka.ms/OfficeSecurityReleases |
| Microsoft | Microsoft Office LTSC 2021 | 16.0.1 < https://aka.ms/OfficeSecurityReleases |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| microsoft | 3.1 | 9.8 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: none
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: added 2025-02-06; federal due date 2025-02-27. Known ransomware use: Unknown.
- CISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
- CISA SSVC assessment: exploitation active, automatable yes, technical impact total.
- FIRST EPSS (model of 2026-10-21): 94.66% probability of exploitation activity in the next 30 days; percentile 99.9.
Timeline
- — CVE record published by microsoft
- — Added to CISA’s Known Exploited Vulnerabilities catalog
- — CISA remediation deadline for US federal agencies
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vendor and project advisories, patches
- Microsoft Outlook Remote Code Execution Vulnerability msrc.microsoft.com
Vulnerability records
- CVE.org record CVE-2024-21413 cve.org
- NVD entry CVE-2024-21413 nvd.nist.gov
Government
Other references from the CVE record and advisory
- vicarius.io vicarius.io
- vicarius.io vicarius.io
- research.checkpoint.com research.checkpoint.com
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