CVE-2026-40359

Microsoft Excel Remote Code Execution Vulnerability

CVE-2026-40359 is fixed in 3 products on 1 platform, first by KB5002865, released May 12, 2026. It is not reported as exploited. Patch Radar priority: High.

High

CVSS

7.8

Important

Exploitation

None reported

Exploitation Less Likely

CISA KEV

Not listed

Not in the Known Exploited Vulnerabilities catalog

EPSS

0.0033

26th percentile

<p>Use after free in Microsoft Office Excel allows an unauthorized attacker to execute code locally.</p>

Where it's fixed

Product	Fix	Released
Microsoft
Microsoft Excel 2016 (32-bit edition)	KB5002865	May 12, 2026
Microsoft Excel 2016 (64-bit edition)	KB5002865	May 12, 2026
Office Online Server	KB5002871	May 12, 2026

Details

Published
May 12, 2026
Weakness
Use After Free
Vendor advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40359

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