Microsoft Windows 11: Elevation of privilege in Container Isolation FS Filter Driver
Summary
The Windows Container Isolation FS Filter Driver (unionfs.sys) in Windows 11 version 26H1 contains an untrusted pointer dereference (CWE-362, CWE-822). An attacker with a local, low-privileged account can exploit it to gain higher privileges, for example SYSTEM rights. Exploitation requires a high attack complexity; the CVSS base score is 7.0 (High). Microsoft's record shows no evidence of exploit code, and the CVE is not yet in CISA KEV.
Affected
- Microsoft Windows 11 version 26H1 (ARM64 and x64)
- Builds 10.0.28000.0 before 10.0.28000.3501
- Other Windows versions: not listed in the CVE record; check the MSRC advisory.
Fixed in
- Fixed in build 10.0.28000.3501 or later.
- Delivering KB number: Unknown.
Workaround
Unknown.
Exploitation
- No known exploitation at publication (CVSS temporal E:U, exploit code maturity unproven).
- No public proof of concept found.
- CISA SSVC: Exploitation none, Automatable no, Technical Impact total.
Our recommendation
- Check the MSRC advisory for the KB number and the complete list of affected products.
- Identify Windows 11 26H1 devices and any Windows container hosts (run winver or check Settings > System > About).
- Install the November 2026 cumulative update and verify the build is 10.0.28000.3501 or later.
- Re-check the CVE for exploit status and KEV listing, as NVD analysis is still pending.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows Container Isolation FS Filter Driver (unionfs.sys)
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Windows
- Updates (KB)
- KB5132059
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-113761 msrc.microsoft.com
- CVE Record: CVE-2026-113761 www.cve.org
- Strix: CVE-2026-113761 www.strix.ai
- Microsoft November 2026 Patch Tuesday (GBHackers) gbhackers.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, 09:03.
Original description (NVD)
Untrusted pointer dereference in Windows Container Isolation FS Filter Driver (unionfs.sys) 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.
Affected? We can help.
We check whether your systems are affected, install updates and close the gap – continuously with the System Health Checker if you wish.