Windows Subsystem for Linux: Buffer overflow leads to local privilege escalation
Summary
A heap-based buffer overflow in Windows Subsystem for Linux (WSL) allows an authorized local user to elevate privileges. Successful exploitation can give the attacker high impact on confidentiality, integrity and availability, potentially up to SYSTEM. Exploitation requires local access with low privileges and is not possible remotely.
Affected
- Windows 10 Version 1809 (before 10.0.17763.9487)
- Windows 10 Version 21H2 (before 10.0.19044.7846)
- Windows 10 Version 22H2 (before 10.0.19045.7846)
- 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 2019, including Server Core (before 10.0.17763.9487)
- Windows Server 2022 (before 10.0.20348.5870)
- Windows Server 2025, including Server Core (before 10.0.26100.33822)
Fixed in
- Fixed in the builds from the Microsoft CNA record: 10.0.17763.9487, 10.0.19044.7846, 10.0.19045.7846, 10.0.22631.7711, 10.0.26100.9974, 10.0.26200.9974, 10.0.28000.3501, 10.0.26300.9974, 10.0.20348.5870, 10.0.26100.33822
- Verify the exact fixed builds and KB numbers in the MSRC advisory. KB numbers: Unknown.
Workaround
Unknown. No workaround was documented in the sources reviewed. Check the FAQ section of the MSRC advisory.
Exploitation
- No evidence of active exploitation found.
- No public proof-of-concept found.
- CISA SSVC: exploitation none, automatable no, technical impact total.
- CISA KEV and GitHub advisory status: not verified.
Our recommendation
- Install the Microsoft security update from the November 2026 Patch Tuesday cycle on all systems with WSL.
- Prioritise hosts with WSL on multi-user machines, jump hosts, build servers and developer laptops with sensitive data.
- Check the MSRC advisory for the exact fixed builds and mitigations.
- Monitor for exploitation signs and for KEV listing.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows Subsystem for Linux
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Windows, Windows ESU (Extended Security Updates)
- Updates (KB)
- KB5131085, KB5131096, KB5131090, KB5131087, KB5132061, KB5132043
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-119834 msrc.microsoft.com
- CVE Record CVE-2026-119834 (CVE.org) www.cve.org
- Strix CVE summary CVE-2026-119834 (third-party) 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, 03:48.
Original description (NVD)
Heap-based buffer overflow in Windows Subsystem for Linux 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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