What is the CVSS score of CVE-2024-21413?

CVE-2024-21413 has a CVSS 3.1 base score of 9.8 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 94.7%.

Is there a public PoC exploit available for CVE-2024-21413?

Yes, a public proof-of-concept exploit is available for CVE-2024-21413. Prioritise patching immediately. EPSS: 94.7%.

Is there a patch available for CVE-2024-21413?

Yes, a patch is available for CVE-2024-21413. Update the affected software to the latest version immediately.

365 Apps CVE-2024-21413

CRITICAL

Improper Input Validation (CWE-20)

2024-02-13 secure@microsoft.com

RCE Microsoft 365 Apps Office Long Term Servicing Channel Office 2019 Office 2016

9.8

CVSS 3.1 · Vendor: microsoft

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Vulnerability Assessment

Weakness	CWE CWE-20 OWASP Top 10:2025 A05:2025 - Injection ASVS 5.0 V2 - Validation and Business Logic Input validation, allowlisting
Impact	CVSS score of 9.8 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. Public proof-of-concept exploit code is available.
Exploit ScenarioDerived	This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the critical-severity affected system.

Act Now Prioritize within 24-48h. Why: In CISA KEV with patch available.

Exploited in the wild (CISA KEV) Patch available 94.7% exploitation probability (EPSS)

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AnalysisAI

Microsoft Outlook Remote Code Execution Vulnerability. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Affects your stack

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Technical ContextAI · show details

This vulnerability is classified under CWE-20. Affected products include: Microsoft 365 Apps, Microsoft Office 2016, Microsoft Office 2019, Microsoft Office Long Term Servicing Channel.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (microsoft) PRIMARY 9.8 CRITICAL

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Primary rating from Vendor (microsoft) · only source for this CVE.

CVSS VectorVendor: microsoft

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Added to CISA KEV

Jul 14, 2026 - 04:22 CISA

CVE Published

Feb 13, 2024 - 18:16 cve.org

CRITICAL 9.8

DescriptionCVE.org

Microsoft Outlook Remote Code Execution Vulnerability

Threat Intelligence Overview

Threat Score

7.8/10

Composite threat intelligence

EPSS Score

94.7%

Top 0% exploitable

Exploit

POC

Public exploit code exists

Data Quality

4 sources

Confidence: Medium

NVD

CVE.org

CISA KEV

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity CRITICAL

CISA KEV Yes

Public POC Yes

EPSS 94.7%

Patch available Yes

Active threat Yes

Deciding rule

In CISA KEV with patch available

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Immediate

Exploitation· derived

Active

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact· derived

High

Priority Score

214

Low Medium High Critical

KEV: +50

EPSS: +95

CVSS: +49

PoC: +20

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Remote Code Execution CRITICAL

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.

Affected Products (CPE)CVE.org

cpe:2.3:a:microsoft:365_apps:-:*:*:*:enterprise:*:*:*

cpe:2.3:a:microsoft:office_2016:-:*:*:*:-:*:x64:*

cpe:2.3:a:microsoft:office_2016:-:*:*:*:-:*:x86:*

cpe:2.3:a:microsoft:office_2019:-:*:*:*:*:*:x64:*

cpe:2.3:a:microsoft:office_2019:-:*:*:*:*:*:x86:*

cpe:2.3:a:microsoft:office_long_term_servicing_channel:2021:*:*:*:*:*:*:*

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References

Advisories & patches

PATCH https://msrc.microsoft.com/update-guide/vulnerability/CVE-2024-21413 REF https://research.checkpoint.com/2024/the-risks-of-the-monikerlink-bug-in-microsoft-outlook-and-the-big-picture/ REF https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-21413 REF https://www.vicarius.io/vsociety/posts/cve-2024-21413-critical-monikerlink-vulnerability-affecting-microsoft-outlook-mitigation-script

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