Windows Installer: Double free leads to local privilege escalation
Summary
A double free in Windows Installer allows an authorized, low-privileged local user to elevate privileges on the affected Windows system. The attack requires local access and a valid account, and the CVSS vector rates attack complexity as High. Successful exploitation can lead to full control of the host.
Affected
- Windows 10 Version 1607, 1809, 21H2, 22H2
- Windows 11 Version 23H2, 24H2, 25H2, 26H1, 26H2
- Windows Server 2016, 2019, 2022 (including Server Core installations)
- Windows Server 2025 and Windows 11 24H2/26H2 entries: verify in 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
- Windows 11 23H2: 10.0.22631.7711
- Windows 11 24H2: 10.0.26100.9974
- Windows 11 25H2: 10.0.26200.9974
- Windows 11 26H1: 10.0.28000.3501
- Windows 11 26H2: 10.0.26300.9974
- Windows Server 2016: 10.0.14393.9688
- Windows Server 2019: 10.0.17763.9487
- Windows Server 2022: 10.0.20348.5870
Fixed in the November 2026 security update. Confirm KB numbers in the MSRC Security Update Guide.
Workaround
Unknown. No workaround is described in the sources.
Exploitation
- Exploitation: none according to Microsoft's CISA SSVC assessment
- Automatable: no
- Public proof of concept: none found
- Exploited in the wild: no evidence found
Our recommendation
- Install the November 2026 cumulative update on all affected systems, with priority on servers and multi-user hosts such as terminal servers and shared workstations
- Restrict who can install MSI packages and keep users on standard (non-admin) accounts
- Monitor for unexpected SYSTEM-level process creation on multi-user hosts
- Several other Windows Installer elevation-of-privilege CVEs were published the same day, so one update should cover them together
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows Installer
- 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, KB5131090, KB5131096, KB5131080, KB5131077, KB5132061
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- CVE.org CVE Record CVE-2026-119399 www.cve.org
- Microsoft Security Update Guide CVE-2026-119399 msrc.microsoft.com
- Rapid7 Patch Tuesday November 2026 summary www.rapid7.com
- EUVD-2026-119399 (Vulners) vulners.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, 08:51.
Original description (NVD)
Double free in Windows Installer 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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