Local code execution via heap overflow
Published Aug 11, 2026 · Updated Aug 25, 2026
Heap-based buffer overflow in Microsoft Office before the August 2026 fixes allows attackers to execute code locally via crafted files. Microsoft's CNA record identifies only a heap overflow and does not disclose the vulnerable Office component, parser, or the operation that overruns the heap on untrusted document data. Exploitation requires user interaction, such as opening or previewing a malicious file, and code runs with the current user's rights rather than as SYSTEM or a server-side service.
Summary
What happened
Heap-based buffer overflow in Microsoft Office before the August 2026 fixes allows attackers to execute code locally via crafted files. Microsoft's CNA record identifies only a heap overflow and does not disclose the vulnerable Office component, parser, or the operation that overruns the heap on untrusted document data. Exploitation requires user interaction, such as opening or previewing a malicious file, and code runs with the current user's rights rather than as SYSTEM or a server-side service.
The record
- CVE
- CVE-2026-63533
- Published
- Aug 11, 2026
- Updated
- Aug 25, 2026
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-122, T1204.002
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 11, 2026CVE publishedPublication date reported by the CVE source.
- Aug 25, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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What is affected?
Affected products and versions are unavailable in this record.
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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