CVE-2026-24307
Published: 22 January 2026
Summary
CVE-2026-24307 is a critical-severity Improper Validation of Specified Type of Input (CWE-1287) vulnerability in Microsoft 365 Copilot. Its CVSS base score is 9.3 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Sharepoint (T1213.002); ranked at the 31.7th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
This vulnerability is AI-related — categorised as Enterprise AI Assistants.
The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Timely application of vendor patches and updates directly remediates the improper input validation flaw in M365 Copilot as detailed in the MSRC guide.
Enforces organization-defined input validation at interfaces to prevent exploitation of improper type validation in user-supplied prompts or files to Copilot.
Receiving and implementing security alerts and directives from Microsoft ensures prompt awareness and action on mitigations for this critical CVE.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The improper input validation in Microsoft 365 Copilot enables crafted prompts/files (delivered via spearphishing attachment/link) to disclose sensitive M365 data like SharePoint content and remote emails, and manipulate stored data integrity.
NVD Description
Improper validation of specified type of input in M365 Copilot allows an unauthorized attacker to disclose information over a network.
Deeper analysisAI
CVE-2026-24307 is an improper validation of specified type of input vulnerability, classified under CWE-1287, affecting Microsoft 365 Copilot. Published on 2026-01-22, it carries a CVSS v3.1 base score of 9.3 (AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N), marking it as critical due to its network accessibility, low complexity, lack of privilege requirements, and potential for high impacts on confidentiality and integrity across a changed scope.
An unauthorized attacker can exploit this vulnerability remotely over the network by tricking a user into interacting with malicious input, such as through a crafted prompt or file. Successful exploitation enables the attacker to disclose sensitive information and potentially manipulate data integrity, though it does not impact availability.
Microsoft's Security Response Center update guide at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-24307 details the vulnerability, including recommended mitigations and available patches.
Details
- CWE(s)
Affected Products
AI Security AnalysisAI
- AI Category
- Enterprise AI Assistants
- Risk Domain
- N/A
- OWASP Top 10 for LLMs 2025
- None mapped
- Classification Reason
- Matched keywords: copilot