Code execution via EMF out-of-bounds write
Published Sep 15, 2021 · Updated Aug 10, 2026
Out-of-bounds write in Microsoft Office Visio in Office 2019 and Microsoft 365 Apps allows attackers to execute code via a crafted EMF file. The Visio EMF parser writes beyond the bounds of allocated memory while processing attacker-controlled image data. Exploitation requires a target to visit a malicious page or open a malicious file; successful code executes in the affected application context.
Summary
What happened
Out-of-bounds write in Microsoft Office Visio in Office 2019 and Microsoft 365 Apps allows attackers to execute code via a crafted EMF file. The Visio EMF parser writes beyond the bounds of allocated memory while processing attacker-controlled image data. Exploitation requires a target to visit a malicious page or open a malicious file; successful code executes in the affected application context.
The record
- CVE
- CVE-2021-38653
- Published
- Sep 15, 2021
- Updated
- Aug 10, 2026
- Vendor
- Microsoft
- Product
- Microsoft Office 2019
- Classifications
- CWE-787, T1203
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 15, 2021CVE publishedPublication date reported by the CVE source.
- Aug 10, 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=19.0.0 <https://aka.ms/OfficeSecurityReleases
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.
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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