Windows Brokering File System: Use-after-free allows local privilege escalation
Summary
A use-after-free vulnerability (CWE-416) in the Windows Brokering File System (bfs.sys) allows an authorized local attacker to elevate privileges. Exploitation requires local access, a low-privilege account and high attack complexity. Microsoft rates the CVE 7.0 (CVSS 3.1, High); NVD analysis is pending, and no exploitation has been reported.
Affected
- Windows 11 Version 24H2: 10.0.26100.0 to before 10.0.26100.9974
- Windows 11 Version 25H2: 10.0.26200.0 to before 10.0.26200.9974
- Windows 11 Version 26H1: 10.0.28000.0 to before 10.0.28000.3501
- Windows 11 Version 26H2: from 10.0.26300.0 (upper build unconfirmed)
- Windows Server 2025 and Server Core installation: 10.0.26100.0 to before 10.0.26100.33822
- Windows 10 and Windows 11 23H2: Unknown.
Fixed in
- Windows 11 24H2: 10.0.26100.9974 or later
- Windows 11 25H2: 10.0.26200.9974 or later
- Windows 11 26H1: 10.0.28000.3501 or later
- Windows Server 2025: 10.0.26100.33822 or later
- Windows 11 26H2: Unconfirmed (a third-party source lists 10.0.26300.9974)
- KB number: Unconfirmed (a third-party source lists KB5132061 for Windows 11 24H2, 25H2 and 26H2)
Workaround
Unknown. No vendor workaround has been identified; applying the security update is the documented remedy.
Exploitation
- Exploited in the wild: no evidence found; CISA SSVC exploitation: none
- Publicly disclosed before the patch: none reported
- Public proof of concept: none found
- CISA KEV: not listed (per a third-party source)
Our recommendation
- Include the November 2026 cumulative updates in the monthly patch cycle, prioritizing Windows Server 2025 hosts, Terminal Servers and shared multi-user endpoints.
- Verify the final fixed builds and KB numbers in the MSRC entry.
- Restrict interactive and local logon on servers, and check endpoints for signs of privilege escalation after phishing or malware incidents.
- Recheck the NVD entry once it has been analyzed.
Information from Microsoft (Patch Tuesday November 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-95979 msrc.microsoft.com
- CVE Record CVE-2026-95979 (Microsoft CNA) www.cve.org
- Tenable: Microsoft November 2026 Patch Tuesday www.tenable.com
- Admin Signal: November 2026 Patch Tuesday priorities www.adminsignal.com
- Cybersecurity News: Windows Brokering File System vulnerability cybersecuritynews.com
- GBHackers: Microsoft Brokering File System vulnerability gbhackers.com
- Strix: CVE-2026-95979 (third-party data) www.strix.ai
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, 07:55.
Original description (NVD)
Use after free in Windows Brokering File System allows an authorized attacker to elevate privileges locally.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
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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