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Medium6.7Microsoft Server

Medium [CVE-2026-21530] Windows Rich Text Edit Elevation of Privilege Vulnerability

This medium-severity Microsoft Server advisory covers CVE-2026-21530 affecting Windows Server 2012 (Server Core installation), Windows Server 2012 R2 (Server Core installation), Windows Server 2016 (Server Core installation).

CVE-2026-21530 Published May 12, 2026Updated by vendor Aug 10, 2026
CVE-2026-21530
Affected products & platforms
Microsoft ServerWindows Server
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Summary

Double free in Windows Rich Text Edit allows an authorized attacker to elevate privileges locally.

Affected products named by the advisory: Windows Server 2012; Windows Server 2012 (Server Core installation); Windows Server 2012 R2; Windows Server 2012 R2 (Server Core installation); and 8 more.

Affected products named by the advisory: Windows Server 2016 (Server Core installation); Windows Server 2019 (Server Core installation); Windows Server 2022, 23H2 Edition (Server Core installation); Windows Server 2025 (Server Core installation).

Affected versions
  • Microsoft 365 Apps for Enterprise 16.0.1 before https://aka.ms/OfficeSecurityReleases
  • Microsoft Office 2016 16.0.0 before 16.0.5556.1000
  • Microsoft Office 2019 19.0.0 before https://aka.ms/OfficeSecurityReleases
  • Microsoft Office LTSC 2021 16.0.1 before https://aka.ms/OfficeSecurityReleases
  • Microsoft Office LTSC 2024 16.0.0 before https://aka.ms/OfficeSecurityReleases
  • Windows 10 Version 1607 10.0.14393.0 before 10.0.14393.9140
  • Windows 10 Version 1809 10.0.17763.0 before 10.0.17763.8755
  • Windows 10 Version 21H2 10.0.19044.0 before 10.0.19044.7291
  • Windows 10 Version 22H2 10.0.19045.0 before 10.0.19045.7417
  • Windows 11 version 23H2 10.0.22631.0 before 10.0.22631.7079
  • Windows 11 Version 23H2 10.0.22631.0 before 10.0.22631.7219
  • Windows 11 Version 24H2 10.0.26100.0 before 10.0.26100.8457

Official advisory · high-confidence parse· fetched 2 hours ago·verify at source

Fixed versions
  • https://aka.ms/OfficeSecurityReleases
  • 16.0.5556.1000
  • 10.0.14393.9140
  • 10.0.17763.8755
  • 10.0.19044.7291
  • 10.0.19045.7417
  • 10.0.22631.7079
  • 10.0.22631.7219
  • 10.0.26100.8457
  • 10.0.26200.8457
  • 10.0.28000.2113
  • 6.2.9200.26079

Official advisory · high-confidence parse· fetched 2 hours ago·verify at source

Mitigation

Upgrade to a fixed release: https://aka.ms/OfficeSecurityReleases, 16.0.5556.1000, 10.0.14393.9140, 10.0.17763.8755, 10.0.19044.7291, 10.0.19045.7417. That is the remediation for this advisory.

The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.

Official advisory · high-confidence parse· fetched 2 hours ago·verify at source

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