Microsoft Windows Installer: Use-after-free elevation of privilege
Summary
A use-after-free flaw in Windows Installer, the component that installs, repairs and removes MSI packages, allows a locally authorized user to elevate privileges. An attacker needs a local low-privilege account, for example after malware or phishing has gained a foothold. Successful exploitation can lead to full compromise of the affected machine (CVSS 7.8).
Affected
- Microsoft Windows 10 Version 1607 (below 10.0.14393.9612)
- Microsoft Windows 10 Version 1809 (below 10.0.17763.9376)
- Microsoft Windows 10 Version 21H2 (below 10.0.19044.7807)
- Microsoft Windows 10 Version 22H2 (build range listed by CNA as below 10.0.19045.7807; verify)
- Microsoft Windows 11 versions 23H2, 24H2, 25H2, 26H1 and 26H2 (see MSRC for exact builds)
- Microsoft Windows Server 2012 and 2012 R2 (including Server Core)
- Microsoft Windows Server 2016 (below 10.0.14393.9612)
Fixed in
- Fixed builds as listed by the CNA record and aggregators: Windows 10 1607 from 10.0.14393.9612; other versions per the list above.
- Not confirmed on MSRC. Unknown: KB number for Windows 10 1607.
- Cumulative update names found for October 2026: KB5126651 (Windows 10 1809 / Server 2019) and KB5126646 (Server 2025). Verify on MSRC.
Workaround
- Unknown. No vendor-documented workaround found.
- Practical measure: limit local logons and restrict software installation to administrators.
Exploitation
- CISA SSVC: exploitation none, automatable no.
- Not listed in CISA KEV (per OpenCVE).
- EPSS about 0.0024.
- No public proof of concept or exploitation reports found in research. This is not proof of absence.
Our recommendation
- Confirm the fixed build and KB for each system on the MSRC Security Update Guide.
- Identify all Windows 10 1607 devices. This build is end-of-life, so plan upgrades; no further fixes are expected beyond the final update.
- Apply the October 2026 cumulative update to all other supported systems.
- Reduce local administrator rights and monitor for unexpected MSI installations.
Information from Microsoft (Patch Tuesday October 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)
- KB5127648, KB5126651, KB5126655, KB5126657, KB5126646, KB5126653
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- MSRC Security Update Guide: CVE-2026-88080 msrc.microsoft.com
- OpenCVE: CVE-2026-88080 app.opencve.io
- Vulners MSCVE: MS:CVE-2026-88080 vulners.com
- Vulners CIRCL: CIRCL:CVE-2026-88080 vulners.com
- Strix: CVE-2026-88080 www.strix.ai
- OffSeq Radar: CVE-2026-88080 radar.offseq.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 2 Nov 2026, 01:28.
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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