Code execution via undisclosed content-processing flaw
Published Jul 14, 2021 · Updated Aug 10, 2026
Remote code execution in affected versions of Microsoft Excel and Office Web Apps Server allows attackers to run code when malicious content is opened. Microsoft has not published the vulnerable component, input format, or operation that processes the content. The required user interaction is the documented gate, and successful exploitation executes code with an otherwise undisclosed security context.
Summary
What happened
Remote code execution in affected versions of Microsoft Excel and Office Web Apps Server allows attackers to run code when malicious content is opened. Microsoft has not published the vulnerable component, input format, or operation that processes the content. The required user interaction is the documented gate, and successful exploitation executes code with an otherwise undisclosed security context.
The record
- CVE
- CVE-2021-34518
- Published
- Jul 14, 2021
- Updated
- Aug 10, 2026
- Vendor
- Microsoft
- Product
- Microsoft Excel 2016
- Classifications
- T1203
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 14, 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=16.0.0.0 <16.0.5188.100
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.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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