CVE record · CVE-2021-26863

Windows Win32k Elevation of Privilege Vulnerability

CVSS 7.0 HighCriticalEPSS 0.12 · 96th percentile

Critical, because:

CVSS score 7.0 (7.0 or more) and EPSS 0.12 (0.1 or more): a high score and a real chance of exploitation in the next 30 days.

Published by the CVE Program (CNA: microsoft) at 11 Mar 2021, 15:37 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

Affected products, as the CNA wrote them
Vendor	Product	Versions
Microsoft	Windows 10 Version 1803	affected 10.0.0 to before 10.0.17134.2087 custom
Microsoft	Windows 10 Version 1809	affected 10.0.17763.0 to before 10.0.17763.1817 custom
Microsoft	Windows 10 Version 1809	affected 10.0.0 to before 10.0.17763.1817 custom
Microsoft	Windows 10 Version 1909	affected 10.0.0 to before 10.0.18363.1440 custom
Microsoft	Windows 10 Version 2004	affected 10.0.0 to before 10.0.19043.867 custom
Microsoft	Windows 10 Version 20H2	affected 10.0.0 to before 10.0.19043.867 custom
Microsoft	Windows Server 2019	affected 10.0.17763.0 to before 10.0.17763.1817 custom
Microsoft	Windows Server 2019 (Server Core installation)	affected 10.0.17763.0 to before 10.0.17763.1817 custom
Microsoft	Windows Server version 2004	affected 10.0.0 to before 10.0.19043.867 custom
Microsoft	Windows Server version 20H2	affected 10.0.0 to before 10.0.19043.867 custom
Microsoft	Windows Server, version 1909 (Server Core installation)	affected 10.0.0 to before 10.0.18363.1440 custom

Identifiers: CVE-2021-26863
CNA: microsoft
Tags: Microsoft Windows 10 Version 1803
Microsoft Windows 10 Version 1809
Microsoft Windows 10 Version 1909
Microsoft Windows 10 Version 2004
Microsoft Windows 10 Version 20H2
Microsoft Windows Server 2019
Microsoft Windows Server 2019 (Server Core installation)
Microsoft Windows Server version 2004
Published: 11 Mar 2021
Updated: 19 Aug 2026

Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
7.0	High	3.1	CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C	CNA (microsoft)

CISA KEV Not listed.
EPSS 0.12, the 96th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

This record came from the full history of the CVE Program, published 11 Mar 2021. New records show when each source confirmed them.

Sources

References from the CNA

msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26863 vendor-advisorypatch

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.