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Windows Projected File System

CVE-2025-55233 — Windows Projected File System Elevation of Privilege Vulnerability

Important CVSS 7.8 EPSS 0.00392 🔬 Patch diffed 2025-12 archive

Executive Summary

Out-of-bounds 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
Exploitation Unlikely
MS Exploit Likelihood
Category Elevation of Privilege
Weakness CWE-125: Out-of-bounds Read
Released Dec 9 2025
Last Updated Dec 9 2025
Publicly Disclosed No
CISA KEV Not Listed
Known Exploits None Known
EPSS Score 0.00392 — 0.32289 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

0.00392
probability of exploitation in the next 30 days
0.32289 percentile - updated 2026-08-14
View on FIRST.org

Affected Products

13 affected products
Product KB Article Severity Impact Restart Required
Windows 10 Version 1809 for 32-bit Systems 5071544 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 1809 for x64-based Systems 5071544 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 21H2 for 32-bit Systems 5071546 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 21H2 for ARM64-based Systems 5071546 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 21H2 for x64-based Systems 5071546 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 22H2 for 32-bit Systems 5071546 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 22H2 for ARM64-based Systems 5071546 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 22H2 for x64-based Systems 5071546 (Security Update) Important Elevation of Privilege Yes
Windows 11 Version 23H2 for ARM64-based Systems 5071417 (Security Update) Important Elevation of Privilege Yes
Windows 11 Version 23H2 for x64-based Systems 5071417 (Security Update) Important Elevation of Privilege Yes
Windows 11 Version 24H2 for ARM64-based Systems 5072033 (Security Update) 5072014 (Security Hotpatch Update) Important Elevation of Privilege 5068861 5068966 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 10.0.26100.7462 10.0.26100.7392 Yes None Windows 11 Version 24H2 for x64-based Systems 5072033 (Security Update) 5072014 (Security Hotpatch Update) Important Elevation of Privilege 5068861 5068966 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 10.0.26100.7462 10.0.26100.7392 Yes None Windows 11 Version 25H2 for ARM64-based Systems 5072033 (Security Update) 5072014 (Security Hotpatch Update) Important Elevation of Privilege 5068861 5068966 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 10.0.26200.7462 10.0.26200.7392 Yes None Windows 11 Version 25H2 for x64-based Systems 5072033 (Security Update) 5072014 (Security Hotpatch Update) Important Elevation of Privilege 5068861 5068966 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 10.0.26200.7462 10.0.26200.7392 Yes None Windows Server 2019 5071544 (Security Update) Important Elevation of Privilege Yes
Windows Server 2019 (Server Core installation) 5071544 (Security Update) Important Elevation of Privilege Yes
Windows Server 2022 5071547 (Security Update) 5071413 (Security Hotpatch Update) Important Elevation of Privilege 5068787 5068840 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 10.0.20348.4529 10.0.20348.4467 Yes None Windows Server 2022 (Server Core installation) 5071547 (Security Update) 5071413 (Security Hotpatch Update) Important Elevation of Privilege 5068787 5068840 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 10.0.20348.4529 10.0.20348.4467 Yes None Windows Server 2022, 23H2 Edition (Server Core installation) 5071542 (Security Update) Important Elevation of Privilege Yes

Patches

4 patches
Article Type Restart
5071544 Security Update Yes
5071546 Security Update Yes
5071417 Security Update Yes
5071542 Security Update Yes

Patch Diff

ghidriff · prjflt.sys (KB5072033)

Out-of-bounds read (CWE-125) in the Windows Projected File System minifilter prjflt.sys PrjfExpandFile, local EoP info-leak. Handling a notification for a file whose path equals the virtualization root, PrjfExpandFile builds the relative path as usRel.Length = FileNameInfo->Name.Length - RootLength - 2. PRE: when the FileObject path is the VirtRoot itself, Name.Length == RootLength+2-ish so the subtraction underflows to 0xFFFE (USHORT), and usRel.Buffer is copied into the command buffer RelPathBuffer with that length; PrjfSendCommandAndWaitForCompletion -> FltSendMessage then sends the command (with ~0xFFFE bytes of relative path) to the user-mode port. Because the FileNameInfo allocation is only 0x160 bytes, the copy over-reads adjacent kernel pool into the message delivered to the user - an info-leak. Diff of prjflt.sys 10.0.26100.7309 -> .7462 (Dec 9 2025, KB5072033) confirms the fix: gated behind CFR flag Feature_3579016506, PrjfExpandFile guards the Name.Length vs RootLength relationship before deriving usRel (rejecting the entry with 0xC0000033 when the name is not strictly longer than the root), so the length can no longer underflow.

Pre-patch version 10.0.26100.7309 Download
Post-patch version 10.0.26100.7462 Download
Function Address Change Note
PrjfExpandFile code change code (bounds/validation added, CFR-gated) Pre: usRel.Length = FileNameInfo->Name.Length - RootLength - 2 underflows to 0xFFFE when the FileObject path == VirtRoot; that length of usRel.Buffer is copied to CommandBuffer->RelPathBuffer and FltSendMessage'd to the user port, over-reading past the 0x160 FileNameInfo pool. Post (Feature_3579016506): the name-vs-root length relationship is validated before usRel is derived (else STATUS_OBJECT_NAME_INVALID 0xC0000033), preventing the underflow.
Feature_3579016506 gate added (CFR gate) CFR flag gating the added validation; the original unchecked path still ships when disabled.
View full diff report View RCA report

Attack Path

A relative-path length is computed as Name.Length - RootLength - 2 and underflows when the file path equals the virtualization root, leaking pool to the user port

Attack path for CVE-2025-55233 A relative-path length is computed as Name.Length - RootLength - 2 and underflows when the file path equals the virtualization root, leaking pool to the user port 01 — ENTRY Local user triggers a ProjFS expansion/notification whose FileObject path is the virtualization root prjflt.sys PrjfExpandFile (via PrjfExpandAndWait / PrjfExpandAndPend) builds a relative path for the notify command. AV:L/PR:L/AC:L. 02 — CONTROLLED INPUT Path length equals the root length, so Name.Length - RootLength - 2 underflows usRel.Length becomes 0xFFFE (USHORT wrap) instead of a small value. 03 — MISSING CHECK 0xFFFE bytes of usRel.Buffer are copied into the command RelPathBuffer (CWE-125) The FileNameInfo pool is only 0x160 bytes, so the copy reads far past it into adjacent pool. 04 — PATH The command buffer is sent to the user-mode port PrjfSendCommandAndWaitForCompletion -> FltSendMessage delivers the ~0xFFFE-byte relative path (with leaked pool) to the user. 05 — PRIMITIVE Adjacent kernel pool disclosed to user mode -> info-leak / EoP The Dec 2025 fix (Feature_3579016506) validates the name-vs-root lengths before deriving usRel, preventing the underflow.

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

Acknowledgments

ChenJian with Sea Security Orca Team

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