CVE-2026-26184 — Windows Projected File System Elevation of Privilege Vulnerability

Executive Summary

Buffer over-read in Windows Projected File System allows an authorized attacker to elevate privileges locally.

Overview

7.8

CVSS HIGH

Important

MS Severity

Not Exploited

MS Exploit Status

Less Likely

MS Exploit Likelihood

Category Elevation of Privilege

Weakness CWE-126: Buffer Over-read

Released Apr 14 2026

Last Updated Apr 14 2026

Publicly Disclosed No

CISA KEV Not Listed

Known Exploits None Known

EPSS Score 0.0024 — 0.15177 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

0.0024

probability of exploitation in the next 30 days

0.15177 percentile - updated 2026-08-14

View on FIRST.org

Affected Products

23 affected products

Product	KB Article	Severity	Impact	Restart Required
Windows 10 Version 1809 for 32-bit Systems	`5082123 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1809 for x64-based Systems	`5082123 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 21H2 for 32-bit Systems	`5082200 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 21H2 for ARM64-based Systems	`5082200 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 21H2 for x64-based Systems	`5082200 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 22H2 for 32-bit Systems	`5082200 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 22H2 for ARM64-based Systems	`5082200 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 22H2 for x64-based Systems	`5082200 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 23H2 for ARM64-based Systems	`5082052 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 23H2 for x64-based Systems	`5082052 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 24H2 for ARM64-based Systems	`5083769 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 24H2 for x64-based Systems	`5083769 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 25H2 for ARM64-based Systems	`5083769 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 25H2 for x64-based Systems	`5083769 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 26H1 for ARM64-based Systems	`5083768 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 version 26H1 for x64-based Systems	`5083768 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2019	`5082123 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2019 (Server Core installation)	`5082123 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2022	`5082142 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2022 (Server Core installation)	`5082142 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2022, 23H2 Edition (Server Core installation)	`5082060 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2025	`5082063 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2025 (Server Core installation)	`5082063 (Security Update)`	Important	Elevation of Privilege	Yes

Patches

8 patches

Article	Type	Restart
`5082123`	Security Update	Yes
`5082200`	Security Update	Yes
`5082052`	Security Update	Yes
`5083769`	Security Update	Yes
`5083768`	Security Update	Yes
`5082142`	Security Update	Yes
`5082060`	Security Update	Yes
`5082063`	Security Update	Yes

Patch Diff

ghidriff · prjflt.sys (KB5083769)

Buffer over-read (CWE-126) in the Windows Projected File System minifilter prjflt.sys PrjfPortConnect, local EoP. The ProjFS filter-port connect callback receives a client _PRJ_CONNECTION_CONTEXT with a VolumeLength field and an inline szVolume (a WCHAR string). PRE: it validated `SizeOfContext >= ConnectionContext->VolumeLength + 0x16`, treating the WCHAR count VolumeLength as a byte length; because szVolume is WCHAR its real byte size is VolumeLength*2, so a client can declare a VolumeLength up to ~2x the real space and still pass, making the UNICODE_STRING built from szVolume extend past the end of the context buffer. That over-read UNICODE_STRING is then used as the ObjectName for ZwCreateFile (via PrjfGetInstanceFromVolumeName -> FltGetVolumeFromName), reading out-of-bounds kernel pool. Diff of prjflt.sys 10.0.26100.8115 -> .8246 (Apr 14 2026, KB5083769) confirms the fix: gated behind CFR flag Feature_3411221816, PrjfPortConnect doubles VolumeLength (sVar5 = sVar5*2, WCHAR->bytes, with an overflow guard (ushort)(sVar5-1)<0x7fff) before the bounds check, so a name that would run past the context is rejected. Note: our diff shows Feature_3411221816 (build/arch); the *2 correction is as described.

Pre-patch version 10.0.26100.8115 Download

Post-patch version 10.0.26100.8246 Download

Function	Address	Change	Note
`PrjfPortConnect`	`code change`	code (VolumeLength doubled for WCHAR in bounds check, CFR-gated)	Pre: if (SizeOfContext >= VolumeLength + 0x16) - WCHAR szVolume validated as bytes -> under-check by 2x, UNICODE_STRING reads past the context. Post (Feature_3411221816): sVar5=VolumeLength; if (feature && (ushort)(sVar5-1)<0x7fff) sVar5=sVar5*2; then require SizeOfContext >= sVar5+0x16.
`Feature_3411221816`	`gate`	added (CFR gate)	CFR flag gating the WCHAR-aware (x2) length check; original under-validating check still ships when disabled.

View full diff report View RCA report

Attack Path

A ProjFS connection context declares a WCHAR volume name validated as bytes, so the name UNICODE_STRING over-reads the context

Derived from the patch delta: the checks added by the vendor identify which fields crossed a trust boundary unvalidated. Reachability and privilege are taken from the call chain in the RCA report.

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

ChenJian with Sea Security Orca Team

References

MSRC Advisory MITRE NVD