Microsoft Windows CNG Key Isolation Service: Elevation of privilege
Summary
A local elevation of privilege vulnerability in the Windows Cryptography Next Generation (CNG) Key Isolation service allows improper memory handling. An attacker who already has code execution on a Windows 10, Windows 11 or Windows Server system can run a specially crafted application to run processes in an elevated context. The attack requires local access and an existing foothold, so the risk is mainly on multi-user systems such as terminal servers, file servers and shared workstations.
Affected
- Windows 10 Version 1607 (builds before 10.0.14393.9688)
- Windows 10 Version 1809 (builds before 10.0.17763.9487)
- Windows 10 Version 21H2 (builds before 10.0.19044.7846)
- Windows 10 Version 22H2 (builds before 10.0.19045.7846)
- Windows 11 Version 23H2 (builds before 10.0.22631.7711)
- Windows 11 Version 24H2 (builds before 10.0.26100.9974)
- Windows 11 Version 25H2 (builds before 10.0.26200.9974)
- Windows 11 Version 26H1 (builds before 10.0.28000.3501)
- Windows 11 Version 26H2 (builds before 10.0.26300.9974)
- Windows Server 2016, including Server Core (builds before 10.0.14393.9688)
- Windows Server 2019, including Server Core (builds before 10.0.17763.9487)
- Windows Server 2022 (builds before 10.0.20348.5870)
Fixed in
- Install the November 2026 security update for the affected Windows version. The fixed build is the first build listed as not affected above.
- KB numbers per build: check the MSRC product table, as they were not confirmed in the sources used.
Workaround
- Unknown. No vendor or third-party workaround was found. Patching is the only documented remedy.
Exploitation
- Microsoft's CVE record marks exploitability as unproven. CISA SSVC lists exploitation as none and automatable as no.
- No public proof of concept was found. The attack must be carried out locally.
- No evidence of exploitation in the wild was found. Verify MSRC's 'Exploited' flag and the CISA KEV catalogue.
Our recommendation
- Apply the November 2026 cumulative update to all affected Windows 10 and Windows Server systems in the next regular patch window. Confirm the KB per build on MSRC.
- Prioritise multi-user systems, terminal servers and file servers.
- Verify that older Windows 10 builds still receive updates (extended support or LTSC) before relying on them.
- Monitor CISA KEV and MSRC exploitability flags, and re-rate if exploitation is reported.
- Note: NVD analysis was pending and the CVSS score (7.0 per CNA) and CWE (CWE-415) may change. VulDB lists 8.8 and CWE-269.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows CNG Key Isolation Service
- 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 Update Guide: CVE-2026-103571 msrc.microsoft.com
- CVE Record CVE-2026-103571 (CVE.org) www.cve.org
- VulDB entry 434348 vuldb.com
- Strix CVE overview CVE-2026-103571 www.strix.ai
- FortiGuard endpoint vulnerability: Windows CNG Key Isolation Service EoP www.fortiguard.com
- Rapid7: CVE-2020-1359 (earlier issue in the same component) www.rapid7.com
- NVD: CVE-2023-28229 (earlier issue in the same component) nvd.nist.gov
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, 09:48.
Original description (NVD)
An elevation of privilege vulnerability exists when the Windows Cryptography Next Generation (CNG) Key Isolation service improperly handles memory. An attacker who successfully exploited this vulnerability could run processes in an elevated context. To exploit this vulnerability, an attacker would first have to gain execution on the victim system. An attacker could then run a specially crafted application to elevate privileges. The security update addresses the vulnerability by correcting how the Windows CNG Key Isolation Service handles memory.
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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