Local code execution via use-after-free
Published May 12, 2026 · Updated May 12, 2026
Use-after-free in Microsoft Office Excel allows local users to execute code when a user opens an attacker-crafted workbook. Microsoft identifies a use-after-free in Excel but has not disclosed the affected parser, object type, or memory-lifetime error sequence. User interaction is required, and successful exploitation runs attacker-controlled code in the context of the user who opens the file.
Summary
What happened
Use-after-free in Microsoft Office Excel allows local users to execute code when a user opens an attacker-crafted workbook. Microsoft identifies a use-after-free in Excel but has not disclosed the affected parser, object type, or memory-lifetime error sequence. User interaction is required, and successful exploitation runs attacker-controlled code in the context of the user who opens the file.
The record
- CVE
- CVE-2026-40359
- Published
- May 12, 2026
- Updated
- May 12, 2026
- Vendor
- Microsoft
- Product
- Microsoft Office LTSC for Mac 2024
- Classifications
- CWE-416, T1203, T1204.002
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 12, 2026CVE publishedPublication date reported by the CVE source.
- May 12, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=16.0.0 <16.109.26051019
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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