365 Apps CVE-2026-26109
HIGHCVSS VectorNVD
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
2DescriptionNVD
Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
AnalysisAI
Arbitrary code execution in Microsoft Office Excel and related products (Office Online Server, 365 Apps) via out-of-bounds memory read allows local attackers to achieve complete system compromise without requiring user interaction or elevated privileges. This high-severity vulnerability affects multiple Microsoft Office components and currently lacks a security patch. …
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RemediationAI
Within 24 hours: Identify all systems running affected Excel versions and restrict file sharing capabilities; communicate vulnerability to all users with guidance on not opening untrusted Excel files. Within 7 days: Deploy network segmentation to limit Excel process privileges, implement file filtering on email gateways to block suspicious Excel attachments, and prepare alternative workflows for critical Excel-dependent processes. …
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