Windows Resilient File System (ReFS): Use-after-free allows local privilege escalation
Summary
A use-after-free flaw in the Windows Resilient File System (ReFS) allows an authorised local attacker to elevate privileges. An attacker needs an existing local foothold, such as a logged-in user account or malware, and the attack is rated high complexity. Successful exploitation could give the attacker high impact on confidentiality, integrity and availability of the system.
Affected
- Windows 11 version 23H2 before 10.0.22631.7711
- Windows 11 version 24H2 before 10.0.26100.9974
- Windows 11 version 25H2 before 10.0.26200.9974
- Windows 11 version 26H1 before 10.0.28000.3501
- Windows 11 version 26H2 before 10.0.26300.9974
- Windows Server 2022 before 10.0.20348.5870
- Windows Server 2025 (including Server Core installation) before 10.0.26100.33822
- Windows 10: Unknown.
Fixed in
- Security updates released with the November 2026 Patch Tuesday cycle, with the fixed builds listed above. Verify the exact builds and KB article numbers in the Microsoft advisory before rollout.
Workaround
Unknown. No vendor-documented mitigation specific to this CVE was found. Apply the security update.
Exploitation
- Exploited in the wild: no evidence found. The CISA KEV catalogue was not checked directly.
- Public proof of concept: none found.
- CISA SSVC: exploitation none, not automatable, total technical impact.
Our recommendation
- Install the November 2026 cumulative update on affected Windows 11 and Windows Server systems in the next patch window, prioritising servers that use ReFS.
- Limit local logon rights on systems that use ReFS.
- Verify the fixed builds in the Microsoft advisory and check the CISA KEV catalogue for later exploitation reports.
- Patch the ReFS component regularly, as several ReFS elevation-of-privilege flaws were published in 2026.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows Resilient File System (ReFS)
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation unlikely
- Product family
- Windows
- Updates (KB)
- KB5131090, KB5131087, KB5132061, KB5132043, KB5131080, KB5131077
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-119386 msrc.microsoft.com
- CVE Record CVE-2026-119386 (Microsoft CNA) www.cve.org
- Strix.ai: CVE-2026-119386 (third party, unverified) www.strix.ai
- Microsoft advisory: CVE-2026-83952 (related ReFS EoP) msrc.microsoft.com
- Microsoft advisory: CVE-2026-50318 (related ReFS EoP) msrc.microsoft.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, 08:52.
Original description (NVD)
Use after free in Windows Resilient File System (ReFS) 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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