CVE-2026-40366

Microsoft Word Remote Code Execution Vulnerability

CVE-2026-40366 is fixed in 2 products on 1 platform, first by KB5002858, released May 12, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

Urgent

CVSS

8.4

Critical

Exploitation

None reported

Exploitation Less Likely

CISA KEV

Not listed

Not in the Known Exploited Vulnerabilities catalog

EPSS

0.0038

32nd percentile

<p>Access of resource using incompatible type ('type confusion') in Microsoft Office Word allows an unauthorized attacker to execute code locally.</p>

Where it's fixed

Product	Fix	Released
Microsoft
Microsoft Word 2016 (32-bit edition)	KB5002858	May 12, 2026
Microsoft Word 2016 (64-bit edition)	KB5002858	May 12, 2026

Details

Published
May 12, 2026
Weakness
Use After Free
Vendor advisory
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40366

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