CVE-2025-27727 — Windows Installer Elevation of Privilege Vulnerability

Executive Summary

Improper link resolution before file access ('link following') in Windows Installer allows an authorized attacker to elevate privileges locally.

Overview

7.8

CVSS HIGH

Important

MS Severity

Not Exploited

MS Exploit Status

More Likely

MS Exploit Likelihood

Category Elevation of Privilege

Weakness CWE-59: Improper Link Resolution Before File Access ('Link Following')

Released Apr 8 2025

Last Updated Apr 8 2025

Publicly Disclosed No

CISA KEV Not Listed

Known Exploits None Known

EPSS Score 0.00911 — 0.56352 percentile

NVD CVSS 7.8 HIGH — matches MSRC

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

ATTACK VECTOR

Local

ATTACK COMPLEXITY

Low

PRIVILEGES REQUIRED

Low

USER INTERACTION

None

SCOPE

Unchanged

CONFIDENTIALITY

High

INTEGRITY

High

AVAILABILITY

High

EXPLOIT CODE MATURITY

Unproven

REMEDIATION LEVEL

Official Fix

REPORT CONFIDENCE

Confirmed

Temporal Score: 6.8

EPSS Score

0.00911

probability of exploitation in the next 30 days

0.56352 percentile - updated 2026-07-25

View on FIRST.org

Affected Products

31 affected products

Product	KB Article	Severity	Impact	Restart Required
Windows 10 for 32-bit Systems	`5055547 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 for x64-based Systems	`5055547 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1607 for 32-bit Systems	`5055521 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1607 for x64-based Systems	`5055521 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1809 for 32-bit Systems	`5055519 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1809 for x64-based Systems	`5055519 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 21H2 for 32-bit Systems	`5055518 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 21H2 for ARM64-based Systems	`5055518 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 21H2 for x64-based Systems	`5055518 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 22H2 for 32-bit Systems	`5055518 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 22H2 for ARM64-based Systems	`5055518 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 22H2 for x64-based Systems	`5055518 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 22H2 for ARM64-based Systems	`5055528 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 22H2 for x64-based Systems	`5055528 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 23H2 for ARM64-based Systems	`5055528 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 23H2 for x64-based Systems	`5055528 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 24H2 for ARM64-based Systems	`5055523 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 24H2 for x64-based Systems	`5055523 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2008 for 32-bit Systems Service Pack 2 5055609 (Monthly Rollup) 5055596 (Security Only) Important Elevation of Privilege 5053888 Base: 7.8 Temporal: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.0.6003.23220 Yes None Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation) 5055609 (Monthly Rollup) 5055596 (Security Only) Important Elevation of Privilege 5053888 Base: 7.8 Temporal: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.0.6003.23220 Yes None Windows Server 2008 for x64-based Systems Service Pack 2 5055609 (Monthly Rollup) 5055596 (Security Only) Important Elevation of Privilege 5053888 Base: 7.8 Temporal: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.0.6003.23220 Yes None Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation) 5055609 (Monthly Rollup) 5055596 (Security Only) Important Elevation of Privilege 5053888 Base: 7.8 Temporal: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.0.6003.23220 Yes None Windows Server 2008 R2 for x64-based Systems Service Pack 1 5055561 (Monthly Rollup) 5055570 (Security Only) Important Elevation of Privilege 5053620 Base: 7.8 Temporal: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.1.7601.27670 Yes None Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation) 5055561 (Monthly Rollup) 5055570 (Security Only) Important Elevation of Privilege 5053620 Base: 7.8 Temporal: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C 6.1.7601.27670 Yes None Windows Server 2012	`5055581 (Monthly Rollup)`	Important	Elevation of Privilege	Yes
Windows Server 2012 (Server Core installation)	`5055581 (Monthly Rollup)`	Important	Elevation of Privilege	Yes
Windows Server 2012 R2	`5055557 (Monthly Rollup)`	Important	Elevation of Privilege	Yes
Windows Server 2012 R2 (Server Core installation)	`5055557 (Monthly Rollup)`	Important	Elevation of Privilege	Yes
Windows Server 2016	`5055521 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2016 (Server Core installation)	`5055521 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2019	`5055519 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2019 (Server Core installation)	`5055519 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2022	`5055526 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2022 (Server Core installation)	`5055526 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2022, 23H2 Edition (Server Core installation)	`5055527 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2025	`5055523 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2025 (Server Core installation)	`5055523 (Security Update)`	Important	Elevation of Privilege	Yes

Patches

10 patches

Article	Type	Restart
`5055547`	Security Update	Yes
`5055521`	Security Update	Yes
`5055519`	Security Update	Yes
`5055518`	Security Update	Yes
`5055528`	Security Update	Yes
`5055523`	Security Update	Yes
`5055581`	Monthly Rollup	Yes
`5055557`	Monthly Rollup	Yes
`5055526`	Security Update	Yes
`5055527`	Security Update	Yes

Patch Diff

ghidriff (PDB symbols resolved from Microsoft symbol server) · msi.dll (KB5055523)

Logic vulnerability — TempPackages registry trust boundary violation in Windows Installer (msi.dll). CMsiTransaction::SetEEUIDirectoryAndFilter unconditionally calls ScheduleFileOrFolderDelete without feature flag check, writing attacker-controlled paths to TempPackages registry. CleanupTempPackagesInternal runs as SYSTEM and calls FDeleteFolder on every TempPackages entry with recursive deletion. Exploitation: C:\Config.Msi delete → NULL DACL re-creation → .rbs rollback script swap → SYSTEM code execution. Patch: Feature_1997029688 check prevents ScheduleFileOrFolderDelete call.

Pre-patch version 5.0.26100.3323 Download

Post-patch version 5.0.26100.3775 Download

Function	Address	Change	Note
`CMsiConfigurationManager::SetEEUIDirectoryAndFilter`	`18018ba10`	code	COM entry point. IsAdmin() check, CreateFileW with DELETE (0x10000), FILE_FLAG_OPEN_REPARSE_POINT (0x200000), calls CMsiTransaction::SetEEUIDirectoryAndFilter
`CMsiTransaction::SetEEUIDirectoryAndFilter`	`18018bb90`	code	VULNERABLE — unconditionally calls ScheduleFileOrFolderDelete without Feature_1997029688 check in pre-patch. Post-patch adds feature flag gate.
`ScheduleFileOrFolderDelete`	`1801af264`	code	CElevate(true), opens TempPackages registry key, writes folder-delete entry via SetValue (vtable 0x30)
`CleanupTempPackagesInternal`	`180186c6c`	code	CElevate(true), enumerates TempPackages, calls FDeleteFolder for entries with folder flag (& 2)
`FDeleteFolder`	`1801b29ac`	code	FindFirstFileW/FindNextFileW loop, DeleteFileW for files, recursive for subdirs, RemoveDirectoryW, LockdownPath + SetFileAttributesW(0) fallback

View full diff report View RCA report Download PoC

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

Simon (@sim0nsecurity)

References

MSRC Advisory MITRE NVD