Windows Installer: Privilege escalation through use after free
Summary
A use-after-free vulnerability in Windows Installer allows an authorized local attacker to elevate privileges, potentially up to SYSTEM level. The attacker needs a valid local account or code already running on the device, and exploitation is rated as high complexity. Successful exploitation would give the attacker full control over the affected system.
Affected
- Windows 10 Version 1607 (builds below 10.0.14393.9688)
- Windows 10 Version 1809 (builds below 10.0.17763.9487)
- Windows 10 Version 21H2 (builds below 10.0.19044.7846)
- Windows 10 Version 22H2 (builds below 10.0.19045.7846)
- Windows 11 Version 23H2 (builds below 10.0.22631.7711)
- Windows 11 Version 24H2 (builds below 10.0.26100.9974)
- Windows 11 Version 25H2 (builds below 10.0.26200.9974)
- Windows 11 Version 26H1 (builds below 10.0.28000.3501)
- Windows 11 Version 26H2 (builds below 10.0.26300.9974)
- Windows Server 2016 incl. Server Core (builds below 10.0.14393.9688)
- Windows Server 2019 incl. Server Core (builds below 10.0.17763.9487)
- Windows Server 2022 (builds below 10.0.20348.5870)
Fixed in
- Security update of the November 2026 Patch Tuesday for the listed Windows versions and builds. Confirm the exact KB numbers on the MSRC page.
Workaround
Unknown.
Exploitation
- No evidence of active exploitation known at the time of writing.
- No public proof-of-concept exploit found.
- CISA SSVC: exploitation none, not automatable, total technical impact.
Our recommendation
- Install the November 2026 Windows security update on all affected systems, prioritizing shared PCs, terminal servers and workstations where untrusted software runs.
- Check whether systems still run Windows 10 1607 or 1809 or Windows Server 2016 or 2019 and whether extended support applies.
- Monitor for reports of exploitation and re-check CISA KEV and the vendor advisory.
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
- Microsoft Security Update Guide: CVE-2026-96027 msrc.microsoft.com
- CVE.org record CVE-2026-96027 www.cve.org
- Strix: CVE-2026-96027 www.strix.ai
- Rapid7: Patch Tuesday November 2026 review www.rapid7.com
- Tenable: Microsoft November 2026 Patch Tuesday www.tenable.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, 07:50.
Original description (NVD)
Use after 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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