Microsoft Windows Win32k: Elevation of privilege via use after free
Summary
A use-after-free flaw in the Win32k kernel driver of Microsoft Windows allows an authorized local user to elevate privileges to SYSTEM. An attacker needs an existing local, low-privileged foothold, and exploitation is considered hard. Microsoft rates the flaw Important and fixed it in the November 2026 Patch Tuesday.
Affected
- Windows 10 Version 1607, 1809, 21H2 and 22H2
- Windows 11 Version 23H2, 24H2, 25H2, 26H1 and 26H2
- Windows Server 2016, 2019 and 2022, including Server Core installations
- Windows Server 2025 (named in a third-party list, not in the CVE record; verify with MSRC)
Fixed in
- Windows 10 1607: 10.0.14393.9688
- Windows 10 1809: 10.0.17763.9487
- Windows 10 21H2: 10.0.19044.7846
- Windows 10 22H2: 10.0.19045.7846 (third-party list)
- Windows 11 23H2: 10.0.22631.7711 (third-party list)
- Windows 11 24H2, 25H2, 26H2: 10.0.26100.9974, 10.0.26200.9974, 10.0.26300.9974 (affected range upper bounds)
- Windows 11 26H1: Unknown.
- Windows Server 2016: 10.0.14393.9688
- Windows Server 2019: 10.0.17763.9487
- Windows Server 2022: 10.0.20348.5870 (third-party list)
- Windows Server 2025: 10.0.26100.33822 (third-party list)
- KB article numbers: Unknown.
Workaround
Unknown. No workaround or mitigation is documented; installing the security update is the only documented remedy.
Exploitation
- Not known to be exploited in the wild (CISA SSVC: exploitation none).
- No public proof of concept known.
- Rapid7 rates exploitation as less likely.
Our recommendation
- Include the fix in the next regular Patch Tuesday cycle (normal priority).
- Install the November 2026 security update on all affected Windows systems, especially multi-user hosts and terminal servers.
- Confirm the fixed build on each machine after installation.
- Check that older Windows 10 systems still receive updates; Extended Security Updates enrolment may be required.
- Obtain the KB numbers and the final build table from MSRC before rollout.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows Win32K
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Windows, Windows ESU (Extended Security Updates)
- Updates (KB)
- KB5131291, KB5131085, KB5131096, KB5131090, KB5131087, KB5132061
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Response Center: CVE-2026-122170 msrc.microsoft.com
- CVE.org record CVE-2026-122170 www.cve.org
- Strix: CVE-2026-122170 www.strix.ai
- BleepingComputer: Microsoft November 2026 Patch Tuesday www.bleepingcomputer.com
- Rapid7: Patch Tuesday November 2026 www.rapid7.com
- GBHackers: Microsoft November 2026 Patch Tuesday 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, 08:23.
Original description (NVD)
Use after free in Windows Win32K 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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