Security readout for executives and security teams
Plain-English summary
This is a critical Microsoft Outlook flaw that can allow remote code execution without user interaction. A successful attack could compromise data, alter systems, or disrupt operations. Organizations using the listed Microsoft 365 and Office editions should treat remediation as urgent.
Executive priority
Immediate. Assign accountable owners, accelerate patch deployment, and track completion across all affected endpoints. CISA KEV inclusion and the 9.8 severity justify emergency handling, especially where Outlook processes untrusted email content.
Technical view
CVE-2024-21413 is an Outlook remote code execution vulnerability categorized as improper input validation (CWE-20). Its CVSS 3.1 score is 9.8: network-accessible, low complexity, no privileges or user interaction required, with high confidentiality, integrity, and availability impact.
Likely exposure
The source bundle identifies Microsoft 365 Apps for Enterprise, Office 2016, Office 2019, and Office LTSC 2021. Exact vulnerable build boundaries are not supplied, so asset and patch status should be verified against Microsoft’s advisory.
Exploitation context
CISA KEV status confirms evidence of exploitation in the wild. The supplied sources do not describe campaign scope, attacker groups, exploitation frequency, or current targeting patterns. The no-user-interaction CVSS assessment increases concern for exposed, unpatched installations.
Researcher notes
The bundle supports critical severity, CWE-20, no-interaction network attackability, and KEV-listed exploitation. It does not provide patch identifiers, precise build ranges, exploit mechanics, indicators of compromise, or campaign attribution. Validate those details directly through Microsoft and CISA before operational use.
Mitigation direction
- Apply Microsoft’s security update for CVE-2024-21413 as an emergency priority.
- Inventory installations of the Microsoft 365 and Office editions identified in the source bundle.
- Follow Microsoft’s advisory for supported versions, update identifiers, and any applicable mitigations.
- Escalate systems that cannot be promptly updated for documented compensating controls.
Validation and detection
- Confirm installed Office and Outlook builds against Microsoft’s CVE-2024-21413 advisory.
- Verify the applicable security update is installed across managed endpoints.
- Rescan endpoints and reconcile results with software inventory and deployment records.
- Investigate failed updates, unmanaged devices, and unsupported installations.
- Review security telemetry for suspicious Outlook-related activity using approved defensive procedures.
Public sources used
The source record changed after analysis: Material source record changed after analysis.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-20: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2024-21413 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- Yes
- Published
Vector: 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
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CISA KEV status
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C3.95.9microsoftVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: 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
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- Added to KEVCISA-ADP
CISA Known Exploited Vulnerabilities metadata lists this CVE as known exploited.
- ADP timelineCISA-ADP
CVE-2024-21413 added to CISA KEV
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
- 2025-02-06T00:00:00.000Z: CVE-2024-21413 added to CISA KEV
Source materials
- CVE List V5 sourceCVE List V5
- Microsoft Outlook Remote Code Execution VulnerabilityCVE reference, microsoft · vendor-advisory, patch
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-21413CVE reference, CISA-ADP · government-resource
- https://www.vicarius.io/vsociety/posts/cve-2024-21413-critical-monikerlink-vulnerability-affecting-microsoft-outlook-mitigation-scriptCVE reference, CVE
- https://www.vicarius.io/vsociety/posts/cve-2024-21413-critical-monikerlink-vulnerability-affecting-microsoft-outlook-detection-scriptCVE reference, CVE
- https://research.checkpoint.com/2024/the-risks-of-the-monikerlink-bug-in-microsoft-outlook-and-the-big-picture/CVE reference, CVE · x_transferred
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.