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Windows Cloud Files Mini Filter Driver: Privilege escalation via TOCTOU race

CVE-2026-119974High 7.0

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Summary

A time-of-check time-of-use (TOCTOU) race condition in the Windows Cloud Files Mini Filter Driver (cldflt.sys) allows a local, authorized user to elevate privileges. The CVSS score is 7.0 (High). Exploitation requires high attack complexity and a foothold on the system, such as a low-privilege user account obtained through phishing or credential theft.

Affected

  • Windows 10 Version 1809 and Windows Server 2019 (incl. Server Core): builds before 10.0.17763.9487
  • Windows 10 Version 21H2: builds before 10.0.19044.7846
  • Windows 10 Version 22H2: builds before 10.0.19045.7846
  • Windows 11 Version 23H2: builds before 10.0.22631.7711
  • Windows 11 Version 24H2 and Windows Server 2025 (incl. Server Core): builds before 10.0.26100.9974 (client) and 10.0.26100.33822 (server)
  • Windows 11 Version 25H2: builds before 10.0.26200.9974
  • Windows 11 Version 26H1: builds before 10.0.28000.3501
  • Windows 11 Version 26H2: builds before 10.0.26300.9974
  • Windows Server 2022: builds before 10.0.20348.5870

Fixed in

Security updates from Microsoft for November 2026 that bring the builds listed above to or beyond the fixed versions. Exact KB numbers: see the MSRC advisory.

Workaround

Unknown. No vendor-specific workaround has been published. Disabling the driver is not verified for this CVE and may break OneDrive Files On-Demand.

Exploitation

  • Exploited in the wild: not identified for this CVE.
  • Public proof of concept: none found.
  • CISA SSVC: exploitation none, not automatable, technical impact total.
  • Related Cloud Files flaws (e.g. CVE-2025-55680) have public exploits, so the driver has a history of local escalation issues.

Our recommendation

  • Install the November 2026 security updates on all affected Windows systems, prioritising multi-user machines, terminal servers and devices with OneDrive sync.
  • Verify the exact fixed builds and KB numbers in the MSRC advisory before rollout.
  • Check that all Windows 10 systems are on supported builds; Windows 10 1809 and 21H2 are out of mainstream support.
  • Monitor for unusual privilege changes and new local administrator accounts.

Information from Microsoft (Patch Tuesday November 2026)

Severity (Microsoft)
Important
Impact
Elevation of privilege – Windows Cloud Files Mini Filter Driver
Status on Patch Tuesday
Neither exploited nor publicly disclosed
Exploitability assessment
Exploitation less likely
Product family
Windows, Windows ESU (Extended Security Updates)
Updates (KB)
KB5131085, KB5131096, KB5131090, KB5131087, KB5132061, KB5132043

Entry in the Microsoft Security Update Guide

Public exploits

PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.

Research sources

Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 11 Nov 2026, 08:25.

Original description (NVD)

Time-of-check time-of-use (toctou) race condition in Windows Cloud Files Mini Filter Driver allows an authorized attacker to elevate privileges locally.

NVD references (1)

Sources

The tracker combines official, freely usable data sources – updated continuously:

This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.

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