OnlyPatch
Windows exFAT File System

CVE-2025-21180 — Windows exFAT File System Remote Code Execution Vulnerability

Important CVSS 7.8 EPSS 0.0093 🔬 Patch diffed 2025-03 archive

Executive Summary

Heap-based buffer overflow in Windows exFAT File System allows an unauthorized attacker to execute code locally.

Overview

7.8
CVSS HIGH
Important
MS Severity
Not Exploited
MS Exploit Status
More Likely
MS Exploit Likelihood
Category Remote Code Execution
Weakness CWE-122: Heap-based Buffer Overflow
Released Mar 11 2025
Last Updated Mar 11 2025
Publicly Disclosed No
CISA KEV Not Listed
Known Exploits None Known
EPSS Score 0.0093 — 0.5751 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:U/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
Unproven
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 6.8

EPSS Score

0.0093
probability of exploitation in the next 30 days
0.5751 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: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/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: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/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: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/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: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/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: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/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: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/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: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/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: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/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: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/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: 6.8 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/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 · exfat.sys (KB5053598)

Integer overflow leading to a heap-based buffer overflow (CWE-122) in the Windows exFAT file-system driver exfat.sys, mount-time arbitrary code execution (Important, RCE, AV:L, UI:R, CVSS 7.8, Exploitation More Likely). When an exFAT volume is mounted, FppSetupAllocationSupport derives the allocation-bitmap support parameters from untrusted on-disk metadata and sizes the in-memory allocation structures. PRE: it took a 32-bit count/length from the volume (param_2 + 0x138) and rounded it up by adding 0xffff WITHOUT an overflow check, so a crafted volume supplying a value near 0xFFFFFFFF wrapped the 32-bit addition to a small number, producing an undersized heap allocation that was then overrun when the structures were populated - a heap overflow reachable at mount time. Because exFAT parses the volume when it is mounted, an attacker who tricks a local user into mounting a malicious VHD (AV:L, UI:R) can trigger the overflow for kernel code execution. Diff of exfat.sys 10.0.26100.2454 -> .3470 (Mar 11 2025, KB5053598) confirms the fix: FppSetupAllocationSupport gains an overflow guard gated behind CFR flag Feature_930095419 - if (uVar7 + 0xffff < uVar7) it sets STATUS_FILE_CORRUPT_ERROR (0xc0000102) and calls ExRaiseStatus() to abort the mount before the undersized allocation is made. (Wide .2454->.3470 span that also linked in CFR feature-usage instrumentation; the security-relevant change is the overflow guard.)

Pre-patch version 10.0.26100.2454 Download
Post-patch version 10.0.26100.3470 Download
Function Address Change Note
FppSetupAllocationSupport code change code (adds +0xffff rounding overflow guard, CFR-gated) Pre: allocation-support size computed as volume_count + 0xffff in 32-bit with no overflow check -> near-UINT_MAX count wraps to a tiny size -> undersized heap allocation -> overflow. Post (Feature_930095419): if (uVar7 + 0xffff < uVar7) set STATUS_FILE_CORRUPT_ERROR (0xc0000102) and ExRaiseStatus() to abort the mount.
DriverEntry code change code (CFR feature registration linked in) DriverEntry and the RtlRegister/RecordFeatureUsage imports were added when this build introduced Feature_930095419 CFR gating to exfat; not the vulnerable code itself.
Feature_930095419 gate added (CFR gate) CFR flag gating the overflow guard in FppSetupAllocationSupport; the original unchecked rounding still ships when the flag is disabled.
View full diff report View RCA report

Attack Path

A crafted exFAT volume overflows the allocation-support size rounding, undersizing a heap buffer that is then overrun at mount

Attack path for CVE-2025-21180 A crafted exFAT volume overflows the allocation-support size rounding, undersizing a heap buffer that is then overrun at mount 01 — ENTRY Victim mounts a specially crafted exFAT volume / VHD exfat!FppSetupAllocationSupport parses the volume metadata at mount time. AV:L / PR:N / UI:R (local, requires the user to mount the image). 02 — CONTROLLED INPUT Volume supplies an allocation count near UINT_MAX The 32-bit count/length at param_2 + 0x138 is taken from the on-disk exFAT metadata and controls the allocation-support size. 03 — MISSING CHECK count + 0xffff rounding overflows (CWE-190 -> CWE-122) The 32-bit +0xffff granularity rounding wraps to a small value, so an undersized heap buffer is allocated for the allocation-support structures. 04 — IMPACT Undersized buffer overrun -> kernel code execution Populating the allocation-support structures writes past the short buffer - a heap overflow in the kernel exFAT driver, exploitable for arbitrary code execution.

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.

Exploits & PoC

Detection Rules

Acknowledgments

George Hughey

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