CVE-2026-81386

Code execution via heap-based buffer overflow

Published Sep 8, 2026 · Updated Sep 10, 2026

Heap-based buffer overflow in Microsoft Excel allows attackers to execute code when a user opens a crafted workbook locally. Microsoft has not published the affected Excel parser, workbook structure, or unchecked operation that overwrites heap memory. Exploitation requires user interaction with a malicious file and executes code in the affected user's security context.

CVSS severity7.8
High
EPSS probability0.35%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in Microsoft Excel allows attackers to execute code when a user opens a crafted workbook locally. Microsoft has not published the affected Excel parser, workbook structure, or unchecked operation that overwrites heap memory. Exploitation requires user interaction with a malicious file and executes code in the affected user's security context.

The record

CVE
CVE-2026-81386
Published
Sep 8, 2026
Updated
Sep 10, 2026
Vendor
Microsoft
Product
Microsoft Office LTSC for Mac 2024
Classifications
CWE-122, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 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.

  1. Affected versionversion=-

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Microsoft · Microsoft Office LTSC for Mac 2024version=-
Microsoft · Microsoft Office 2016version=16.0.0 <16.0.5569.1003
Microsoft · Microsoft Office 2019version=19.0.0 <16.0.10417.20207
Microsoft · Microsoft Excel 2016version=16.0.0.0 <16.0.5569.1003
Microsoft · Microsoft Office LTSC for Mac 2021version=-
Microsoft · Microsoft Office 365 for Macversion=-
Microsoft · Microsoft Office LTSC 2021version=16.0.1 <16.0.14334.20906
Microsoft · Microsoft Office LTSC 2024version=16.0.0 <16.0.17932.20976
Microsoft · Microsoft 365 Apps for enterpriseversion=16.0.1 <16.0.20326.20138

Published CVSS scores

7.8MicrosoftCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8MicrosoftCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
T1204.002User Execution: Malicious File

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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