Windows Fast FAT File System Driver Remote Code Execution Vulnerability (CVE-2025-24985)
Published In CISA KEV since Sources: pwn.watch, CVE.org, Msrc Update Guide
What is affected, what to do
Integer overflow or wraparound in Windows Fast FAT Driver allows an unauthorized attacker to execute code locally.
The vulnerability is being actively exploited; treat it as a priority. Update Microsoft Windows 10 Version 1507 to version 10.0.10240.20947, Microsoft Windows 10 Version 1607 to version 10.0.14393.7876, Microsoft Windows 10 Version 1809 to version 10.0.17763.7009. Immediate actions, mitigation and detection rules are in the runbook below.
- Affected
- Microsoft Windows 10 Version 1507
lt 10.0.10240.0..10.0.10240.20947 - Microsoft Windows 10 Version 1607
lt 10.0.14393.0..10.0.14393.7876 - Microsoft Windows 10 Version 1809
lt 10.0.17763.0..10.0.17763.7009 - Microsoft Windows 10 Version 21H2
lt 10.0.19044.0..10.0.19044.5608 - Microsoft Windows 10 Version 22H2
lt 10.0.19045.0..10.0.19045.5608 - Microsoft Windows 11 version 22H2
lt 10.0.22621.0..10.0.22621.5039 - Microsoft Windows 11 version 22H3
lt 10.0.22631.0..10.0.22631.5039 - Microsoft Windows 11 Version 23H2
lt 10.0.22631.0..10.0.22631.5039 - Microsoft Windows 11 Version 24H2
lt 10.0.26100.0..10.0.26100.3476 - Microsoft Windows Server 2008 R2 Service Pack 1
lt 6.1.7601.0..6.1.7601.27618 - Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation)
lt 6.1.7601.0..6.1.7601.27618 - Microsoft Windows Server 2008 Service Pack 2
lt 6.0.6003.0..6.0.6003.23168 - Microsoft Windows Server 2008 Service Pack 2 (Server Core installation)
lt 6.0.6003.0..6.0.6003.23168 - Microsoft Windows Server 2012
lt 6.2.9200.0..6.2.9200.25368 - Microsoft Windows Server 2012 (Server Core installation)
lt 6.2.9200.0..6.2.9200.25368 - Microsoft Windows Server 2012 R2
lt 6.3.9600.0..6.3.9600.22470 - Microsoft Windows Server 2012 R2 (Server Core installation)
lt 6.3.9600.0..6.3.9600.22470 - Microsoft Windows Server 2016
lt 10.0.14393.0..10.0.14393.7876 - Microsoft Windows Server 2016 (Server Core installation)
lt 10.0.14393.0..10.0.14393.7876 - Microsoft Windows Server 2019
lt 10.0.17763.0..10.0.17763.7009 - Microsoft Windows Server 2019 (Server Core installation)
lt 10.0.17763.0..10.0.17763.7009 - Microsoft Windows Server 2022
lt 10.0.20348.0..10.0.20348.3328 - Microsoft Windows Server 2022, 23H2 Edition (Server Core installation)
lt 10.0.25398.0..10.0.25398.1486 - Microsoft Windows Server 2025
lt 10.0.26100.0..10.0.26100.3476 - Microsoft Windows Server 2025 (Server Core installation)
lt 10.0.26100.0..10.0.26100.3476
- Microsoft Windows 10 Version 1507
- Fixed in
- Microsoft Windows 10 Version 1507
10.0.10240.20947 - Microsoft Windows 10 Version 1607
10.0.14393.7876 - Microsoft Windows 10 Version 1809
10.0.17763.7009 - Microsoft Windows 10 Version 21H2
10.0.19044.5608 - Microsoft Windows 10 Version 22H2
10.0.19045.5608 - Microsoft Windows 11 version 22H2
10.0.22621.5039 - Microsoft Windows 11 version 22H3
10.0.22631.5039 - Microsoft Windows 11 Version 23H2
10.0.22631.5039 - Microsoft Windows 11 Version 24H2
10.0.26100.3476 - Microsoft Windows Server 2008 R2 Service Pack 1
6.1.7601.27618 - Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation)
6.1.7601.27618 - Microsoft Windows Server 2008 Service Pack 2
6.0.6003.23168 - Microsoft Windows Server 2008 Service Pack 2 (Server Core installation)
6.0.6003.23168 - Microsoft Windows Server 2012
6.2.9200.25368 - Microsoft Windows Server 2012 (Server Core installation)
6.2.9200.25368 - Microsoft Windows Server 2012 R2
6.3.9600.22470 - Microsoft Windows Server 2012 R2 (Server Core installation)
6.3.9600.22470 - Microsoft Windows Server 2016
10.0.14393.7876 - Microsoft Windows Server 2016 (Server Core installation)
10.0.14393.7876 - Microsoft Windows Server 2019
10.0.17763.7009 - Microsoft Windows Server 2019 (Server Core installation)
10.0.17763.7009 - Microsoft Windows Server 2022
10.0.20348.3328 - Microsoft Windows Server 2022, 23H2 Edition (Server Core installation)
10.0.25398.1486 - Microsoft Windows Server 2025
10.0.26100.3476 - Microsoft Windows Server 2025 (Server Core installation)
10.0.26100.3476
- Microsoft Windows 10 Version 1507
Not sure whether and how you are affected? Ask a question about this vulnerability
Metrics
7.8
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: NVD, CVSS v3
7.8
CVSS v3
Severity High on the scale from 0 to 10.
Source: pwn.watch, CVE.org, Msrc Update Guide
3.9 %
EPSS score
Moderate — model estimates 1-10% exploitation likelihood.
Source: FIRST EPSS, percentile 90.2
Show all metrics
- Severity
- Critical
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 212.23 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- actively exploitedSource: VulnCheck KEV (opens in a new tab) How we classify
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 7.8 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 7.8
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 3.9 %
- Moderate — model estimates 1-10% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 90.2
- Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- Actively exploited
- Published
In CISA KEV since
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossaryCWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-190, CWE-122
Response and mitigation
Why act now?
Prioritisation rationale
Microsoft fixed this as an actively exploited zero-day in the March 2025 Patch Tuesday release, and CISA added it to KEV the same day. Exploitation needs local access and user interaction but no prior authentication. Success yields full confidentiality, integrity and availability impact at kernel level. The realistic delivery path is a phishing-borne crafted VHD aimed at office and admin workstations, often chained with other bugs. Exploitation likelihood is well above the CVE baseline, and CISA has no known ransomware use on record. Treat it as high priority for all user-facing Windows endpoints (patch within days and document it for NIS2 evidence), and as medium priority for servers without interactive users.
Runbook step 1
Immediate response (0-24 h)
-
Roll out the March 2025 Patch Tuesday updates to all Windows endpoints and servers. Target builds:
- Windows 10 1507 ≥ 10.0.10240.20947
- Windows 10 1607 ≥ 10.0.14393.7876
- Windows 10 1809 ≥ 10.0.17763.7009
- Windows 10 21H2/22H2 ≥ 10.0.19044.5608 / 10.0.19045.5608
- Windows 11 22H2 ≥ 10.0.22621.5039
- Windows 11 23H2 ≥ 10.0.22631.5039
The context does not supply KB numbers. A patch is available from the vendor — look up the KB ID in Microsoft's advisory for CVE-2025-24985, and verify Server SKU coverage there as well.
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Verify compliance from inventory (Intune/SCCM/WSUS build reporting). Raise tickets for any host below the target build.
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Patch high-exposure systems first: mail- and web-facing user workstations, multi-user VDI/RDS hosts, admin workstations and jump hosts.
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Block or quarantine disk-image attachments and downloads (
.vhd,.vhdx,.img,.iso) at the mail gateway and web proxy now. Microsoft describes exploitation as a local user mounting a crafted virtual disk. -
Send a short user advisory, especially in OT-adjacent and critical-infrastructure teams: do not mount unknown image files or USB media.
-
Runbook step 2
Mitigation layers
- Mail/perimeter: Make the disk-image block permanent. In Exchange Online, add
vhd,vhdx,imgandisoto the common attachment filter. Inspect archives (ZIP/7z) for embedded images. - Endpoint hardening: Stop standard users from double-click mounting
.vhd/.vhdx. Either remap the file association via GPO or remove the "Mount" shell verb. RestrictMount-DiskImageanddiskpartfor non-admins with AppLocker/WDAC. - Removable media: Where operationally feasible, enforce "Removable Storage Access: Deny all" or device-installation restrictions. This shrinks the attack surface from crafted FAT-formatted USB media.
- Driver disable (test first): Where FAT volumes are not needed, set
HKLM\SYSTEM\CurrentControlSet\Services\fastfat→Start=4. This is not a vendor recommendation. It breaks FAT/FAT32 support for USB sticks, SD cards and mounted EFI partitions, so use it only as a temporary compensating control. - Least privilege: Remove local admin rights and enforce LAPS. This limits lateral movement via reused local credentials after a successful exploit.
- Mail/perimeter: Make the disk-image block permanent. In Exchange Online, add
Runbook step 3
Detection rules
- File telemetry (Sysmon EID 11 / MDE): Flag disk images landing in user-writable paths. KQL:
DeviceFileEvents | where FileName endswith ".vhd" or FileName endswith ".vhdx" | where FolderPath has_any ("Downloads","Content.Outlook","INetCache","Temp") - Mount activity: Monitor the
Microsoft-Windows-VHDMP/Operationalchannel. Also watch process creation (Sysmon EID 1 / Security 4688) forMount-DiskImage,diskpartwithattach vdisk, or Explorer-initiated VHD mounts by non-admin accounts. Correlate with a recent mail or browser download. - Privilege escalation: Alert on SYSTEM-integrity processes spawned from a medium-integrity parent shortly after an image mount. Sigma shape:
process_creation | IntegrityLevel: System AND ParentIntegrityLevel: Medium AND ParentImage NOT IN (services.exe, svchost.exe). - Crash indicators: System log Event ID 1001 (BugCheck) or 41 (Kernel-Power) referencing
fastfat.sysmay indicate failed exploitation attempts. PreserveMEMORY.DMPand minidumps for forensics. - EDR ancestry: Watch for the chain
outlook.exe/browser →explorer.exemount → execution from a newly assigned drive letter. Treat execution from dynamically mounted volumes as a dedicated alert.
- File telemetry (Sysmon EID 11 / MDE): Flag disk images landing in user-writable paths. KQL:
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
Integer overflow or wraparound in Windows Fast FAT Driver allows an unauthorized attacker to execute code locally.
Source: pwn.watch, NVD (NIST), Microsoft Security Update Guide, cvelistv5, CISA KEV Catalog, CVE.org (MITRE)
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| Microsoft | Windows 10 Version 1507 |
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| Microsoft | Windows 10 Version 1607 |
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| Microsoft | Windows 10 Version 1809 |
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| Microsoft | Windows 10 Version 21H2 |
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| Microsoft | Windows 10 Version 22H2 |
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| Microsoft | Windows 11 version 22H2 |
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| Microsoft | Windows 11 version 22H3 |
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| Microsoft | Windows 11 Version 23H2 |
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| Microsoft | Windows 11 Version 24H2 |
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| Microsoft | Windows Server 2008 R2 Service Pack 1 |
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| Microsoft | Windows Server 2008 R2 Service Pack 1 (Server Core installation) |
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| Microsoft | Windows Server 2008 Service Pack 2 |
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| Microsoft | Windows Server 2008 Service Pack 2 (Server Core installation) |
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| Microsoft | Windows Server 2012 |
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| Microsoft | Windows Server 2012 (Server Core installation) |
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| Microsoft | Windows Server 2012 R2 |
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| Microsoft | Windows Server 2012 R2 (Server Core installation) |
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| Microsoft | Windows Server 2016 |
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| Microsoft | Windows Server 2016 (Server Core installation) |
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| Microsoft | Windows Server 2019 |
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| Microsoft | Windows Server 2019 (Server Core installation) |
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| Microsoft | Windows Server 2022 |
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| Microsoft | Windows Server 2022, 23H2 Edition (Server Core installation) |
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| Microsoft | Windows Server 2025 |
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| Microsoft | Windows Server 2025 (Server Core installation) |
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Vendors and products
- Microsoft Windows 10 1507
- Microsoft Microsoft Windows 10 1607
- Microsoft Microsoft Windows 10 1809
- Microsoft Microsoft Windows 10 21H2
- Microsoft Microsoft Windows 10 22h2
- Microsoft Windows 10 Version 1507
- Microsoft Windows 10 Version 1607
- Microsoft Windows 10 Version 1809
- Microsoft Windows 10 Version 21h2
- Microsoft Windows 10 Version 22h2
- Microsoft Microsoft Windows 11 22H2
- Microsoft Microsoft Windows 11 23H2
Affected operating systems
| Windows | microsoft | windows_10_1507 | — |
| Windows | microsoft | windows_10_1607 | — |
| Windows | microsoft | windows_10_1809 | — |
| Windows | microsoft | windows_10_21h2 | — |
| Windows | microsoft | windows_10_22h2 | — |
| Windows | microsoft | windows_11_22h2 | — |
| Windows | microsoft | windows_11_23h2 | — |
| Windows | microsoft | windows_11_24h2 | — |
| Windows | microsoft | windows_server_2008 | r2 |
| Windows | microsoft | windows_server_2008 | — |
| Windows | microsoft | windows_server_2012 | r2 |
| Windows | microsoft | windows_server_2012 | — |
| Windows | microsoft | windows_server_2016 | — |
| Windows | microsoft | windows_server_2019 | — |
| Windows | microsoft | windows_server_2022 | — |
| Windows | microsoft | windows_server_2022_23h2 | — |
| Windows | microsoft | windows_server_2025 | — |
Weakness classes (CWE)
CWE-190Integer Overflow or Wraparound
Base
The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.
Entry at MITRE CWE-190CWE-122Heap-based Buffer Overflow
Variant
A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
Entry at MITRE CWE-122
Public exploit references
Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.
| CISA KEV Catalog | CISA Known Exploited Vulnerability (opens in a new tab)cisa.gov | actively exploited |
References & sources
- Microsoft Security Update GuideWindows Fast FAT File System Driver Remote Code Execution VulnerabilityVendor advisory, Patch, Patch, Vendor advisory
- cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2025-24985government-resource, US government resource
- vicarius.iovsociety/posts/cve-2025-24985-integer-overflow-vulnerability-in…Mitigation, Third-party advisory
- vicarius.iovsociety/posts/cve-2025-24985-integer-overflow-vulnerability-in…Exploit, Third-party advisory
- pwn.watchpwn.watch: Microsoft Windows: 6 exploited vulnerabilities (CVE-2025-24983, CVE-2025-24984, CVE-2025-24985, CVE-2025-24991, CVE-2025-24993, CVE-2025-26633)pwn-watch
- Microsoft Security Update GuideMicrosoft advisory: Microsoft Windowspwn-watch
- Microsoft Security Update GuideMicrosoft advisory: Microsoft Windowspwn-watch
- Microsoft Security Update GuideMicrosoft advisory: Microsoft Windowspwn-watch
- Microsoft Security Update GuideMicrosoft advisory: Microsoft Windowspwn-watch
- Microsoft Security Update GuideMicrosoft advisory: Microsoft Windowspwn-watch
- NVD (NIST)NVD: CVE-2025-24983pwn-watch
- NVD (NIST)NVD: CVE-2025-24984pwn-watch
- NVD (NIST)NVD: CVE-2025-24985pwn-watch
- NVD (NIST)NVD: CVE-2025-24991pwn-watch
- NVD (NIST)NVD: CVE-2025-24993pwn-watch
- NVD (NIST)NVD: CVE-2025-26633pwn-watch
- cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
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<a href="https://intel.neosec.eu/en/cve/CVE-2025-24985"><img src="https://intel.neosec.eu/badge/cve/CVE-2025-24985.svg?lang=en" alt="CVE-2025-24985 – NEOSEC Intel" height="20"></a>