OnlyPatch
Windows Fast FAT Driver

CVE-2025-24985 — Windows Fast FAT File System Driver Remote Code Execution Vulnerability

Important CVSS 7.8 EPSS 0.03846 ⚠️ Exploited in the wild 🔬 Patch diffed 2025-03 archive

Executive Summary

Integer overflow or wraparound in Windows Fast FAT Driver allows an unauthorized attacker to execute code locally.

Overview

7.8
CVSS HIGH
Important
MS Severity
Exploited
MS Exploit Status
Exploitation Detected
MS Exploit Likelihood
Category Remote Code Execution
Weakness CWE-190: Integer Overflow or Wraparound
Released Mar 11 2025
Last Updated Mar 11 2025
Publicly Disclosed No
CISA KEV Not Listed
Known Exploits None Known
EPSS Score 0.03846 — 0.89194 percentile
NVD CVSS 7.8 HIGH — matches MSRC

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
ATTACK VECTOR
Local
ATTACK COMPLEXITY
Low
PRIVILEGES REQUIRED
None
USER INTERACTION
Required
SCOPE
Unchanged
CONFIDENTIALITY
High
INTEGRITY
High
AVAILABILITY
High
EXPLOIT CODE MATURITY
Functional
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 7.2

EPSS Score

0.03846
probability of exploitation in the next 30 days
0.89194 percentile - updated 2026-08-14
View on FIRST.org

Affected Products

25 affected products
Product KB Article Severity Impact Restart Required
Windows 10 for 32-bit Systems 5053618 (Security Update) Important Remote Code Execution Yes
Windows 10 for x64-based Systems 5053618 (Security Update) Important Remote Code Execution Yes
Windows 10 Version 1607 for 32-bit Systems 5053594 (Security Update) Important Remote Code Execution Yes
Windows 10 Version 1607 for x64-based Systems 5053594 (Security Update) Important Remote Code Execution Yes
Windows 10 Version 1809 for 32-bit Systems 5053596 (Security Update) Important Remote Code Execution Yes
Windows 10 Version 1809 for x64-based Systems 5053596 (Security Update) Important Remote Code Execution Yes
Windows 10 Version 21H2 for 32-bit Systems 5053606 (Security Update) Important Remote Code Execution Yes
Windows 10 Version 21H2 for ARM64-based Systems 5053606 (Security Update) Important Remote Code Execution Yes
Windows 10 Version 21H2 for x64-based Systems 5053606 (Security Update) Important Remote Code Execution Yes
Windows 10 Version 22H2 for 32-bit Systems 5053606 (Security Update) Important Remote Code Execution Yes
Windows 10 Version 22H2 for ARM64-based Systems 5053606 (Security Update) Important Remote Code Execution Yes
Windows 10 Version 22H2 for x64-based Systems 5053606 (Security Update) Important Remote Code Execution Yes
Windows 11 Version 22H2 for ARM64-based Systems 5053602 (Security Update) Important Remote Code Execution Yes
Windows 11 Version 22H2 for x64-based Systems 5053602 (Security Update) Important Remote Code Execution Yes
Windows 11 Version 23H2 for ARM64-based Systems 5053602 (Security Update) Important Remote Code Execution Yes
Windows 11 Version 23H2 for x64-based Systems 5053602 (Security Update) Important Remote Code Execution Yes
Windows 11 Version 24H2 for ARM64-based Systems 5053598 (Security Update) 5053636 (SecurityHotpatchUpdate) Important Remote Code Execution 5051987 5052105 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 10.0.26100.3476 10.0.26100.3403 Yes None Windows 11 Version 24H2 for x64-based Systems 5053598 (Security Update) 5053636 (SecurityHotpatchUpdate) Important Remote Code Execution 5051987 5052105 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 10.0.26100.3476 10.0.26100.3403 Yes None Windows Server 2008 for 32-bit Systems Service Pack 2 5053888 (Monthly Rollup) 5053995 (Security Only) Important Remote Code Execution 5052038 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 6.0.6003.23168 Yes None Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation) 5053888 (Monthly Rollup) 5053995 (Security Only) Important Remote Code Execution 5052038 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 6.0.6003.23168 Yes None Windows Server 2008 for x64-based Systems Service Pack 2 5053888 (Monthly Rollup) 5053995 (Security Only) Important Remote Code Execution 5052038 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 6.0.6003.23168 Yes None Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation) 5053888 (Monthly Rollup) 5053995 (Security Only) Important Remote Code Execution 5052038 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 6.0.6003.23168 Yes None Windows Server 2008 R2 for x64-based Systems Service Pack 1 5053620 (Monthly Rollup) 5053627 (Security Only) Important Remote Code Execution 5052016 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 6.1.7601.27618 Yes None Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation) 5053620 (Monthly Rollup) 5053627 (Security Only) Important Remote Code Execution 5052016 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 6.1.7601.27618 Yes None Windows Server 2012 5053886 (Monthly Rollup) Important Remote Code Execution Yes
Windows Server 2012 (Server Core installation) 5053886 (Monthly Rollup) Important Remote Code Execution Yes
Windows Server 2012 R2 5053887 (Monthly Rollup) Important Remote Code Execution Yes
Windows Server 2012 R2 (Server Core installation) 5053887 (Monthly Rollup) Important Remote Code Execution Yes
Windows Server 2016 5053594 (Security Update) Important Remote Code Execution Yes
Windows Server 2016 (Server Core installation) 5053594 (Security Update) Important Remote Code Execution Yes
Windows Server 2019 5053596 (Security Update) Important Remote Code Execution Yes
Windows Server 2019 (Server Core installation) 5053596 (Security Update) Important Remote Code Execution Yes
Windows Server 2022 5053603 (Security Update) 5053638 (SecurityHotpatchUpdate) Important Remote Code Execution 5051979 5052106 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 10.0.20348.3328 10.0.20348.3270 Yes None Windows Server 2022 (Server Core installation) 5053603 (Security Update) 5053638 (SecurityHotpatchUpdate) Important Remote Code Execution 5051979 5052106 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 10.0.20348.3328 10.0.20348.3270 Yes None Windows Server 2022, 23H2 Edition (Server Core installation) 5053599 (Security Update) Important Remote Code Execution Yes

Patches

8 patches
Article Type Restart
5053618 Security Update Yes
5053594 Security Update Yes
5053596 Security Update Yes
5053606 Security Update Yes
5053602 Security Update Yes
5053886 Monthly Rollup Yes
5053887 Monthly Rollup Yes
5053599 Security Update Yes

Patch Diff

ghidriff · fastfat.sys (KB5053598)

Patch diff 10.0.26100.1150 -> 10.0.26100.3470 (24H2 KB5053598; fastfat allocation integer-overflow checks)

Pre-patch version 10.0.26100.1150
Post-patch version 10.0.26100.3470
Function Address Change Note
__GSHandlerCheck 1c000df18 -> 1c000ea08 refcount, address similarity 1.0
DriverEntry 1c0066078 -> 1c0067078 code, length, sig, address, called similarity 0.15
NTOSKRNL.EXE::IoDeleteDevice EXTERNAL:0000008e -> EXTERNAL:00000097 refcount, address similarity 1.0
FatExamineFatEntries 1c0027538 -> 1c0028538 code, length, address, called similarity 0.36
__security_check_cookie 1c000e120 -> 1c000ec10 refcount, address, calling similarity 1.0
NTOSKRNL.EXE::ExRaiseStatus EXTERNAL:00000102 -> EXTERNAL:0000010e refcount, address, calling similarity 1.0
FatSetupAllocationSupport 1c00291a0 -> 1c002a1f8 code, length, address, called similarity 0.22
View full diff report View RCA report Download PoC

Attack Path

Integer overflow in FAT32 cluster accounting reached by mounting a crafted VHD

Attack path for CVE-2025-24985 Integer overflow in FAT32 cluster accounting reached by mounting a crafted VHD 01 — ENTRY Victim opens or mounts a malicious VHD file A VHD mounts with standard user rights; the file can arrive by download or share. fastfat.sys parses it automatically. 02 — CONTROLLED INPUT Boot sector BPB fields are set to overflow the cluster computation NumberOfSector32 = 0xFFFFFFFF, SectorsPerFat32 = 0x80000000, ReservedSectors = 4, SectorsPerCluster = 1 so no division reduces the result. 03 — PATH Mounting drives the allocation-support setup FatSetupAllocationSupport computes NumberOfClusters = (NumberOfSector32 - NumberOfFatTables * SectorsPerFat32 - ReservedSectors) / SectorsPerCluster. 04 — MISSING CHECK No overflow validation on the subtraction or the multiply NumberOfFatTables * SectorsPerFat32 overflows and the subtraction underflows, producing a wildly wrong cluster count that then sizes downstream allocations. The patch adds explicit allocation integer-overflow checks. 05 — PRIMITIVE Undersized allocation followed by writes sized from the true cluster count Pool corruption from a file the victim merely opened. Rated RCE by Microsoft; exploited in the wild.

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

Anonymous

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