Local privilege escalation via heap buffer overflow
Published Feb 10, 2026 · Updated Feb 10, 2026
Heap-based buffer overflow in Microsoft Office Excel allows local users to elevate privileges after required user interaction. Microsoft identifies Excel's heap handling as the affected locus but has not disclosed the malformed input, parser path, or out-of-bounds write operation. Successful exploitation grants elevated privileges on the affected host; remote, interaction-free exploitation is not supported.
Summary
What happened
Heap-based buffer overflow in Microsoft Office Excel allows local users to elevate privileges after required user interaction. Microsoft identifies Excel's heap handling as the affected locus but has not disclosed the malformed input, parser path, or out-of-bounds write operation. Successful exploitation grants elevated privileges on the affected host; remote, interaction-free exploitation is not supported.
The record
- CVE
- CVE-2026-21259
- Published
- Feb 10, 2026
- Updated
- Feb 10, 2026
- Vendor
- Microsoft
- Product
- Microsoft Office 2019
- Classifications
- CWE-787, CWE-122, T1068
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Feb 10, 2026CVE publishedPublication date reported by the CVE source.
- Feb 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?
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- 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.
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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