Microsoft ActiveX Installer Service: Local privilege escalation
Summary
A local elevation of privilege flaw in the Microsoft ActiveX Installer Service, caused by use of an uninitialized resource, is fixed in the November 2026 Windows updates. An authorized local user with low privileges could gain higher privileges on an affected system, with high impact on confidentiality, integrity and availability. The flaw is not remotely exploitable, and an attacker would first need a foothold such as a compromised user account or malware running as a user.
Affected
- Windows 10 Version 1607 (before 10.0.14393.9688)
- 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 2016, including Server Core (before 10.0.14393.9688)
- Windows Server 2019, including Server Core (before 10.0.17763.9487)
- Windows Server 2022 (before 10.0.20348.5870)
Fixed in
Fixed in the November 2026 Windows updates. The fixed builds are the version numbers listed under affected, as stated in the CVE record. Confirm them against the MSRC advisory before rollout.
Workaround
Unknown. No Microsoft workaround was found.
Exploitation
- Not known to be exploited; no public proof of concept found.
- CISA SSVC: exploitation none, automatable no, technical impact total.
- The CVSS exploit maturity is rated unproven.
Our recommendation
- Inventory all Windows 10, 11 and Server systems and confirm their exact build numbers.
- Install the November 2026 Windows updates, starting with multi-user systems, terminal servers and hosts still running unsupported Windows 10 builds.
- Check whether older Windows 10 builds are still serviced in your environment.
- Apply least privilege and restrict local logon rights where practical.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Microsoft ActiveX Installer 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-2026-96158 msrc.microsoft.com
- CVE Record: CVE-2026-96158 www.cve.org
- Rapid7: November 2026 Patch Tuesday review www.rapid7.com
- BleepingComputer: November 2026 Patch Tuesday www.bleepingcomputer.com
- OffSeq Radar: CVE-2026-96158 radar.offseq.com
- Strix: CVE-2026-96158 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, 07:34.
Original description (NVD)
Use of uninitialized resource in Microsoft ActiveX Installer Service 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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