CVE-2026-21253 — Mailslot File System Elevation of Privilege Vulnerability

Executive Summary

Use after free in Mailslot File System allows an authorized attacker to elevate privileges locally.

Overview

7

CVSS HIGH

Important

MS Severity

Not Exploited

MS Exploit Status

More Likely

MS Exploit Likelihood

Category Elevation of Privilege

Released Feb 10 2026

Last Updated Feb 10 2026

Publicly Disclosed No

CISA KEV Not Listed

Known Exploits None Known

EPSS Score 0.00767 — 0.50706 percentile

CVSS Vector

ATTACK VECTOR

Local

ATTACK COMPLEXITY

High

PRIVILEGES REQUIRED

Low

USER INTERACTION

None

SCOPE

Unchanged

Temporal Score: 6.1

EPSS Score

0.00767

probability of exploitation in the next 30 days

0.50706 percentile - updated 2026-06-20

View on FIRST.org

Affected Products

31 affected products

Product	KB Article	Severity	Impact	Restart Required
Windows 10 Version 1607 for 32-bit Systems	`5075999 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1607 for x64-based Systems	`5075999 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1809 for 32-bit Systems	`5075904 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1809 for x64-based Systems	`5075904 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 21H2 for 32-bit Systems	`5075912 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 21H2 for ARM64-based Systems	`5075912 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 21H2 for x64-based Systems	`5075912 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 22H2 for 32-bit Systems	`5075912 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 22H2 for ARM64-based Systems	`5075912 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 22H2 for x64-based Systems	`5075912 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 23H2 for ARM64-based Systems	`5075941 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 23H2 for x64-based Systems	`5075941 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 24H2 for ARM64-based Systems	`5077181 (Security Update) 5077212 (Security Hotpatch Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 24H2 for x64-based Systems	`5077212 (Security Hotpatch Update) 5077181 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 25H2 for ARM64-based Systems	`5077181 (Security Update) 5077212 (Security Hotpatch Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 25H2 for x64-based Systems	`5077181 (Security Update) 5077212 (Security Hotpatch Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 26H1 for ARM64-based Systems	`5077179 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 version 26H1 for x64-based Systems	`5077179 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2012	`5075971 (Monthly Rollup)`	Important	Elevation of Privilege	Yes
Windows Server 2012 (Server Core installation)	`5075971 (Monthly Rollup)`	Important	Elevation of Privilege	Yes
Windows Server 2012 R2	`5075970 (Monthly Rollup)`	Important	Elevation of Privilege	Yes
Windows Server 2012 R2 (Server Core installation)	`5075970 (Monthly Rollup)`	Important	Elevation of Privilege	Yes
Windows Server 2016	`5075999 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2016 (Server Core installation)	`5075999 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2019	`5075904 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2019 (Server Core installation)	`5075904 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2022	`5075906 (Security Update) 5075943 (Security Hotpatch Update)`	Important	Elevation of Privilege	Yes
Windows Server 2022 (Server Core installation)	`5075906 (Security Update) 5075943 (Security Hotpatch Update)`	Important	Elevation of Privilege	Yes
Windows Server 2022, 23H2 Edition (Server Core installation)	`5075897 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2025	`5075899 (Security Update) 5075942 (Security Hotpatch Update)`	Important	Elevation of Privilege	Yes
Windows Server 2025 (Server Core installation)	`5075899 (Security Update) 5075942 (Security Hotpatch Update)`	Important	Elevation of Privilege	Yes

Patches

12 patches

Article	Type	Restart
`5075999`	Security Update	Yes
`5075904`	Security Update	Yes
`5075912`	Security Update	Yes
`5075941`	Security Update	Yes
`5077181 (Security Update) 5077212`	Security Update	Yes
`5077212 (Security Hotpatch Update) 5077181`	Security Hotpatch Update	Yes
`5077179`	Security Update	Yes
`5075971`	Monthly Rollup	Yes
`5075970`	Monthly Rollup	Yes
`5075906 (Security Update) 5075943`	Security Update	Yes
`5075897`	Security Update	Yes
`5075899 (Security Update) 5075942`	Security Update	Yes

Known Exploits

No known exploits have been linked for this CVE yet. When available, exploit references will be sourced from public repositories and may be unverified, incomplete, or non-functional. Always review code carefully before use in any environment.

Acknowledgments

Anonymous

References

MSRC Advisory MITRE NVD