CVE tracker / CVE-2026-33840
CVE-2026-33840
CVE-2026-33840 is the Win32k Elevation of Privilege Vulnerability. Microsoft rates it Important, CVSS 7.8. It is not in CISA's Known Exploited Vulnerabilities catalog. Published May 12, 2026.
Risk summary
HighElevation of Privilege
7.8
CVSS v3 base
2.0%
EPSS: chance of exploitation in 30 days
High
Severity
Important
Microsoft's rating
More Likely
Microsoft: exploitation
No
In CISA KEV
Microsoft describes it: “Use after free in Windows Win32K - ICOMP allows an authorized attacker to elevate privileges locally.”
How to fix it
Microsoft lists 8 affected products and the update that fixes each:
- KB5087539 · fixed build 10.0.26100.32860
Windows Server 2025, Windows Server 2025 (Server Core installation) - KB5089548 · fixed build 10.0.28000.2113
Windows 11 Version 26H1 for ARM64-based Systems, Windows 11 version 26H1 for x64-based Systems - KB5089549 · fixed build 10.0.26100.8457, 10.0.26200.8457
Windows 11 Version 24H2 for x64-based Systems, Windows 11 Version 24H2 for ARM64-based Systems, Windows 11 Version 25H2 for x64-based Systems, Windows 11 Version 25H2 for ARM64-based Systems
What Microsoft changed
- May 19, 2026: Acknowledgement added. This is an informational change only.
- June 23, 2026: Updated an acknowledgement. This is an informational change only.
- May 12, 2026: Information published.
Details
- Weakness
- CWE-416: Use After Free
- Publicly disclosed (Microsoft)
- No
- Exploited (Microsoft)
- No
- Known exploited (CISA KEV)
- Not listed
- Published
- May 12, 2026
- Last revised
- June 23, 2026
Get told when this changes
Senserva Watch emails Microsoft security and patch alerts when something moves: a new exploitation report, a revised fix, a known issue. Free, one email address.
References
From Microsoft, CISA, NVD and FIRST data; the Microsoft details were read when this page was opened. Check the references above before you act.