CVE-2026-83991

mediumpriority · track · 32OT risk · elevatedEPSS 0.003 · 23 %ileexploit · PoCDERUUS

grimoire priorityP1 · Urgent

Exploitable?

Public exploit

2 exploits · PoC

Likely / severe?

0.30% (23rd) EPSS

CVSS 5.5 · medium

Is it mine?

75 products

Check your exposure

Who says so?

3 sources

fstec_bdu · cert_bund · msrc_csaf

EPSS · scored 2026-10-27

Missing authentication for critical function in Windows Cloud Files Mini Filter Driver allows an authorized attacker to perform tampering locally.

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

A vendor fix is available.

FixedWindows 10 Version 1809 for 32-bit Systemsmsrc_csaf
10.0.17763.9245:Security Update:https://support.microsoft.com/help/5122876
https://support.microsoft.com/help/5122876
FixedWindows 10 Version 1809 for x64-based Systemsmsrc_csaf
10.0.17763.9245:Security Update:https://support.microsoft.com/help/5122876
https://support.microsoft.com/help/5122876
FixedWindows 10 Version 21H2 for 32-bit Systemsmsrc_csaf
10.0.19044.7725:Security Update:https://support.microsoft.com/help/5122878
https://support.microsoft.com/help/5122878
FixedWindows 10 Version 21H2 for ARM64-based Systemsmsrc_csaf
10.0.19044.7725:Security Update:https://support.microsoft.com/help/5122878
https://support.microsoft.com/help/5122878
FixedWindows 10 Version 21H2 for x64-based Systemsmsrc_csaf
10.0.19044.7725:Security Update:https://support.microsoft.com/help/5122878
https://support.microsoft.com/help/5122878
FixedWindows 10 Version 22H2 for 32-bit Systemsmsrc_csaf
10.0.19045.7725:Security Update:https://support.microsoft.com/help/5122878
https://support.microsoft.com/help/5122878
FixedWindows 10 Version 22H2 for ARM64-based Systemsmsrc_csaf
10.0.19045.7725:Security Update:https://support.microsoft.com/help/5122878
https://support.microsoft.com/help/5122878
FixedWindows 10 Version 22H2 for x64-based Systemsmsrc_csaf
10.0.19045.7725:Security Update:https://support.microsoft.com/help/5122878
https://support.microsoft.com/help/5122878
FixedWindows 11 Version 23H2 for ARM64-based Systemsmsrc_csaf
10.0.22631.7582:Security Update:https://support.microsoft.com/help/5122880
https://support.microsoft.com/help/5122880
FixedWindows 11 Version 23H2 for x64-based Systemsmsrc_csaf
10.0.22631.7582:Security Update:https://support.microsoft.com/help/5122880
https://support.microsoft.com/help/5122880
FixedWindows 11 Version 24H2 for ARM64-based Systemsmsrc_csaf
10.0.26100.9445:Security Update:https://support.microsoft.com/help/5124008
https://support.microsoft.com/help/5124008
FixedWindows 11 Version 24H2 for x64-based Systemsmsrc_csaf
10.0.26100.9445:Security Update:https://support.microsoft.com/help/5124008
https://support.microsoft.com/help/5124008
FixedWindows 11 Version 25H2 for ARM64-based Systemsmsrc_csaf
10.0.26200.9445:Security Update:https://support.microsoft.com/help/5124008
https://support.microsoft.com/help/5124008
FixedWindows 11 Version 25H2 for x64-based Systemsmsrc_csaf
10.0.26200.9445:Security Update:https://support.microsoft.com/help/5124008
https://support.microsoft.com/help/5124008
FixedWindows 11 Version 26H1 for ARM64-based Systemsmsrc_csaf
10.0.28000.2954:Security Update:https://support.microsoft.com/help/5124012
https://support.microsoft.com/help/5124012
FixedWindows 11 version 26H1 for x64-based Systemsmsrc_csaf
10.0.28000.2954:Security Update:https://support.microsoft.com/help/5124012
https://support.microsoft.com/help/5124012
FixedWindows Server 2019msrc_csaf
10.0.17763.9245:Security Update:https://support.microsoft.com/help/5122876
https://support.microsoft.com/help/5122876
FixedWindows Server 2019 (Server Core installation)msrc_csaf
10.0.17763.9245:Security Update:https://support.microsoft.com/help/5122876
https://support.microsoft.com/help/5122876
FixedWindows Server 2022msrc_csaf
10.0.20348.5622:Security Update:https://support.microsoft.com/help/5122882
https://support.microsoft.com/help/5122882
FixedWindows Server 2022 (Server Core installation)msrc_csaf
10.0.20348.5622:Security Update:https://support.microsoft.com/help/5122882
https://support.microsoft.com/help/5122882
FixedWindows Server 2025msrc_csaf
10.0.26100.33438:Security Update:https://support.microsoft.com/help/5122871
https://support.microsoft.com/help/5122871
FixedWindows Server 2025 (Server Core installation)msrc_csaf
10.0.26100.33438:Security Update:https://support.microsoft.com/help/5122871
https://support.microsoft.com/help/5122871

cvss

Technical severity, 0–10. One row per scoring source.

5.5

010

base score 0–10 · higher = more severe · hover a vector to decode

v3.15.5mediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:Nprimary · secure@microsoft.com USexploitability 1.8 · impact 3.6

v3.15.5mediumAV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:Nsecondary · FSTEC (BDU) RU

v3.15.2mediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N/E:Psecondary · CVSS-BT (t0sche)

v3.15.5mediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N/E:U/RL:O/RC:Csecondary · Microsoft Security Response Center US

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Trackcoordinatorcisa_ssvcUS

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-306USCWE-306USCWE-306US

exploits (2)

Public proof-of-concept and weaponised exploit code.

ZeroDayVPN/CVE-2026-83991-WriteUP-and-PoCZeroDayVPN/CVE-2026-83991-WriteUP-and-PoCPoC · poc_in_github
karollooool/CVE-2026-83991-writeup-and-pocCVE-2026-83991: Windows Cloud Files access-check bypassPoC · poc_in_github

affected products (75)

Products and version ranges known to be affected.

Microsoft Windows 10all versionscert_bundDEcpe:/o:microsoft:windows_10:-
Microsoft Windows 11all versionscert_bundDEcpe:/o:microsoft:windows_11:-
Microsoft Windows Server 2012all versionscert_bundDEcpe:/o:microsoft:windows_server_2012:-
Microsoft Windows Server 2012 R2all versionscert_bundDEcpe:/o:microsoft:windows_server_2012_r2:-
Microsoft Windows Server 2016all versionscert_bundDEcpe:/o:microsoft:windows_server_2016:-
Microsoft Windows Server 2019all versionscert_bundDEcpe:/o:microsoft:windows_server_2019:-
Microsoft Windows Server 2022all versionscert_bundDEcpe:/o:microsoft:windows_server_2022:-
Microsoft Windows Server 2025all versionscert_bundDEcpe:/o:microsoft:windows_server_2025:-
Microsoft Corp Windows 10 1809≤ 10.0.17763.9245fstec_bduRU
Microsoft Corp Windows 10 21H2≤ 10.0.19044.7725fstec_bduRU
Microsoft Corp Windows 10 22H2≤ 10.0.19045.7725fstec_bduRU
Microsoft Corp Windows 11 23H2≤ 10.0.22631.7582fstec_bduRU
Microsoft Corp Windows 11 24H2≤ 10.0.26100.9445fstec_bduRU
Microsoft Corp Windows 11 25H2≤ 10.0.26200.9445fstec_bduRU
Microsoft Corp Windows 11 26H1≤ 10.0.28000.2954fstec_bduRU
Microsoft Corp Windows Server 2019≤ 10.0.17763.9245fstec_bduRU
Microsoft Corp Windows Server 2019 (Server Core installation)≤ 10.0.17763.9245fstec_bduRU
Microsoft Corp Windows Server 2022≤ 10.0.20348.5622fstec_bduRU
Microsoft Corp Windows Server 2022 (Server Core installation)≤ 10.0.20348.5622fstec_bduRU
Microsoft Corp Windows Server 2025≤ 10.0.26100.33438fstec_bduRU

showing 20 of 75

advisories (2)

Vendor and ecosystem advisories describing this.

WID-SEC-W-2026-3243Microsoft Windows: Mehrere SchwachstellenDeutsch2026-09-08csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in verschiedenen Versionen von Microsoft Windows Server, Microsoft Windows 10 und Microsoft Windows 11 ausnutzen, um seine Privilegien zu erhöhen, um einen Denial of Service herbeizuführen, um Informationen offenzulegen und um beliebigen Code auszuführen.
msrc_CVE-2026-83991Windows Cloud Files Mini Filter Driver Tampering Vulnerability2026-09-08csaf · msrc_csafUS
To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle

also known as (1)

Other names and identifiers for this entity.

BDU:2026-14537 fstec_bdu

sources

Which sources assert this record, and when.

fstec_bdu cert_bund msrc_csaf NVD CVE.org MITRE

published 2026-09-08modified 2026-09-14

references (1) nvd

External citations — patches, advisories, analysis.

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-83991Vendor AdvisoryPatch

scry

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