Windows Installer: Security feature bypass due to improper signature verification
Summary
Windows Installer, the Windows component that installs, maintains and removes MSI packages, does not properly verify cryptographic signatures (CWE-347). An attacker who can deliver a crafted installer package may bypass a security feature on an affected Windows system. Exploitation requires user interaction, and the impact is limited to integrity according to the CVSS vector (5.3, Medium).
Affected
- Windows 10 Version 1607 and Windows Server 2016 (including Server Core): before 10.0.14393.9688
- Windows 10 Version 1809 and Windows Server 2019 (including Server Core): 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 2022: before 10.0.20348.5870
Fixed in
- Security updates from the November 2026 Patch Tuesday for the affected Windows versions, with the build numbers listed above or higher. Verify the exact KB numbers on the Microsoft Security Update Guide.
Workaround
Unknown.
Exploitation
- Microsoft's CVSS vector carries E:U (unproven exploit maturity).
- CISA SSVC: exploitation none, not automatable.
- Rapid7 rates exploitation as less likely; no public disclosure or known public proof of concept found at the time of writing.
- Not found in the CISA KEV catalog in the research search; recheck the catalog.
Our recommendation
- Install the November 2026 security updates on all affected Windows 10, Windows 11 and Windows Server systems, prioritising end-of-support Windows 10 builds (1607, 1809, 21H2) on Extended Security Updates.
- Verify the build numbers on the Microsoft Security Update Guide before rollout.
- Restrict who can run installers on servers and workstations, enforce least privilege and use application control where possible.
- Train users not to open unknown MSI files or installers received by email or downloads.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Security feature bypass – 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)
- 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-2026-119867 msrc.microsoft.com
- CVE.org record CVE-2026-119867 www.cve.org
- Rapid7: Patch Tuesday November 2026 www.rapid7.com
- BleepingComputer: Microsoft November 2026 Patch Tuesday www.bleepingcomputer.com
- Senserva KB5131085 (third-party) senserva.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, 18:32.
Original description (NVD)
Improper verification of cryptographic signature in Windows Installer allows an unauthorized attacker to bypass a security feature over a network.
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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