Home/CVE/Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to elevate privileges locally.
CVE

CVE-2026-21259

Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to elevate privileges locally.

Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to elevate privileges locally.

HIGH · CVSS 7.8 EPSS 0.00031
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  • CVSS base score ≥ 7.0
Sigma rules13 YARA rules0
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Weakness Classification

CWE-122Heap-based Buffer Overflow
CWE-787Out-of-bounds Write
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Affected Products & Versions

5
microsoft 365 appsall versions
microsoft excelall versions
microsoft officeall versions
microsoft office long term servicing channelall versions
microsoft office online server< 16.0.10417.20097
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Sigma Hunt Rules

13
Exact rules name this CVE ID. Product rules name an affected product in their title. Related rules cover techniques used by actors who exploited this CVE. Showing the most relevant matches; the complete related set is on the full drill-down.
producthighSuspicious Microsoft Office Child Process - MacOS
producthighCode Executed Via Office Add-in XLL File
producthighPotential Persistence Via Microsoft Office Add-In
producthighPotential Persistence Via Microsoft Office Startup Folder
producthighFile With Uncommon Extension Created By An Office Application
producthighOffice Macro File Creation From Suspicious Process
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Scoring & Timeline

7.8
HIGH · CVSS v3.1 · secure@microsoft.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD10 Feb 2026 · 06:16 PM
CVSS VectorCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
no
Technical impact
total
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
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Vendor Advisories

1
msrcCVE-2026-21259Elevation of Privilege
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