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Microsoft Security Response CenterCVE-2026-64909

Microsoft Office Remote Code Execution Vulnerability

Integer underflow (wrap or wraparound) in Microsoft Office allows an unauthorized attacker to execute code locally.

Read the vendor bulletin Get alerts for Microsoft Office 365 for Mac
7.8CVSS out of 10Critical severity
Scope

What the vendor says is affected

  • Microsoft Office 365 for Mac
  • Microsoft Office 2019 for 32-bit editions
  • Microsoft Office 2019 for 64-bit editions
  • Microsoft 365 Apps for Enterprise for 32-bit Systems
  • Microsoft 365 Apps for Enterprise for 64-bit Systems
  • Microsoft Office LTSC for Mac 2021
  • Microsoft Office LTSC 2021 for 64-bit editions
  • Microsoft Office LTSC 2021 for 32-bit editions
  • Microsoft Office LTSC 2024 for 32-bit editions
  • Microsoft Office LTSC 2024 for 64-bit editions
  • Microsoft Office LTSC for Mac 2024
  • Microsoft Office 2016 (32-bit edition)
  • Microsoft Office 2016 (64-bit edition)

Versions the vendor lists as fixed

  • 16.112.26081010
  • https://aka.ms/OfficeSecurityReleases
  • 16.0.5565.1001
Next step

What the vendor recommends

Release Notes Click to Run Install KB5002897.

Review the complete instructions on the vendor's site
Update history

What changed in later vendor updates

SecurityAlert records field-level changes from the point we begin following a bulletin. Earlier vendor changes may not have a field-by-field record.

    • The vendor changed its remediation guidance.
Timeline

When this advisory changed

  1. Published by Microsoft Security Response Center

    The publication date reported by the vendor.

  2. Added to SecurityAlert

    We collected the advisory from the official source.

  3. Confirmed at the source

    Our collector saw this advisory during a later source check.

Vulnerabilities

CVEs named in this advisory

CVE-2026-64909View CVSS, KEV, EPSS, and threat context
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