Windows 11 Brokering File System: Local privilege escalation
Summary
The Windows Brokering File System (bfs.sys), which manages file, pipe and registry access for sandboxed applications, contains a flaw caused by release of an invalid pointer or reference (CWE-763). An authorized local attacker with low privileges can elevate privileges to a higher level on the affected system. The attack complexity is high and no user interaction is required, but the attacker first needs local code execution, for example through malware or untrusted software run by a user.
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: 10.0.26300.0 to before 10.0.26300.9974
- Windows Server, Windows 10 and Windows 11 23H2: Unknown.
Fixed in
- Windows 11 24H2, 25H2 and 26H2: November 2026 cumulative update (build 10.0.26100.9974, 10.0.26200.9974 and 10.0.26300.9974 or later).
- Windows 11 26H1: build 10.0.28000.3501 or later.
- Reported KB5132061 (SSU KB5132688) for Windows 11 24H2, 25H2 and 26H2; not yet confirmed against the MSRC entry.
Workaround
- Unknown. No vendor workaround is documented in the sources reviewed.
- Patching is the available fix.
Exploitation
- Exploitation in the wild: not known for this CVE.
- Public proof-of-concept: none known.
- CISA SSVC: exploitation none, not automatable, technical impact total.
- Not found in the CISA Known Exploited Vulnerabilities list.
Our recommendation
- Install the November 2026 cumulative update on all Windows 11 24H2, 25H2 and 26H2 devices and on affected servers. Verify the cumulative update build, not only the KB number.
- Prioritize workstations and shared or multi-user endpoints where untrusted software is run.
- Restrict untrusted code execution and keep users on standard accounts until patched.
- Monitor for unexpected privilege changes and new local administrator accounts.
Information from Microsoft (Patch Tuesday November 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- MSRC Security Update Guide msrc.microsoft.com
- CVE.org record www.cve.org
- Third-party CVE summary (versions) www.strix.ai
- November 2026 Patch Tuesday, KB and exploitation status www.adminsignal.com
- November 2026 Patch Tuesday, exploited zero-day www.rescana.com
- BFS component context cybersecuritynews.com
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, 07:38.
Original description (NVD)
Release of invalid pointer or reference 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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