Microsoft security update for CVE-2026-21509
🔗 CVE IDs covered (1)
📋 Microsoft's advisory
EchelonGraph does not copy Microsoft's advisory page: its FAQ and remediation text are not shown here. Read the advisory on https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509. This page also shows what EchelonGraph holds for CVE-2026-21509, with the description from its CVE record, which the CVE Numbering Authority that assigned the CVE wrote: for a CVE Microsoft assigned, often in the words of Microsoft's own advisory.
🎯 Affected products10
- Microsoft 365 Apps for Enterprise for 32-bit Systems
- Microsoft 365 Apps for Enterprise for 64-bit Systems
- Microsoft Office 2016 (32-bit edition)
- Microsoft Office 2016 (64-bit edition)
- Microsoft Office 2019 for 32-bit editions
- Microsoft Office 2019 for 64-bit editions
- Microsoft Office LTSC 2021 for 32-bit editions
- Microsoft Office LTSC 2021 for 64-bit editions
- Microsoft Office LTSC 2024 for 32-bit editions
- Microsoft Office LTSC 2024 for 64-bit editions
✅ Updates Microsoft lists: 3 updates
3 rows: one per KB article or update, update type and fixed build. Their details are on Microsoft's advisory.
| KB article | Update | Fixed build |
|---|---|---|
| — | Security Update | 16.0.10417.20095 |
| — | Security Update | release notes |
| — | Security Update | 16.0.5539.1001 |
🧭 EchelonGraph on CVE-2026-21509
- EchelonGraph score
- 9.0 CRITICAL
- CISA KEV
- Listed since January 26, 2026
- Fix status
- A fix is available — apply it.
Description from the CVE record (CVE.org), as published by its numbering authority
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
Published by Microsoft Corporation, the CVE Numbering Authority that assigned CVE-2026-21509, in its CVE record at CVE.org; reused under the CVE Program's Terms of Use (its licence and MITRE's copyright notice are in our Terms of Service).
🔗 References (5)
- advisoryhttps://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509
- referencehttps://learn.microsoft.com/en-us/officeupdates/update-history-office-2019
- referencehttps://docs.microsoft.com/en-us/officeupdates/office365-proplus-security-updates
- patchhttps://www.microsoft.com/en-us/download/details.aspx?id=108535
- referencehttps://support.microsoft.com/help/5002713