Windows Installer: Elevation of privilege via stack-based buffer overflow
Summary
A stack-based buffer overflow in Windows Installer allows an authorized local user to elevate privileges on the affected Windows system. The attack requires local access with low privileges and no user interaction, so it is not directly exposed to the internet. It is most relevant when an attacker already has a foothold, for example through a phished or low-privilege account.
Affected
- Windows 10 Version 1607 (builds below 10.0.14393.9612)
- Windows 10 Version 1809 (builds below 10.0.17763.9376)
- Windows 10 Version 21H2 (builds below 10.0.19044.7807)
- Windows 10 Version 22H2 (builds below 10.0.19045.7807)
- Windows 11 Version 23H2 (builds below 10.0.22631.7652)
- Windows 11 Version 24H2 (builds below 10.0.26100.9711)
- Windows 11 Version 25H2 (builds below 10.0.26200.9711)
- Windows 11 Version 26H1 (builds below 10.0.28000.3231)
- Windows 11 Version 26H2 (builds below 10.0.26300.9711)
- Windows Server 2012 (builds below 6.2.9200.26434), including Server Core
- Windows Server 2012 R2 (builds below 6.3.9600.23470), including Server Core
- Windows Server 2016 (builds below 10.0.14393.9612)
Fixed in
- Updates with the builds listed above, released by Microsoft on 13 October 2026, according to the CNA record.
- The KB numbers for Windows 10 Version 1607 and Windows Server 2016 are unknown and must be confirmed in the MSRC table.
Workaround
Unknown. No vendor workaround or mitigation was found. Interim measures, based on general practice rather than the advisory:
- Restrict local logon on affected systems to necessary users.
- Limit installation rights for standard users.
Exploitation
- No public proof of concept found.
- No exploitation in the wild known.
- CISA SSVC: exploitation none, automatable no, technical impact total.
- EPSS 0.0024 (very low).
Our recommendation
- Install the October 2026 security updates on all affected Windows systems, prioritising shared and legacy machines.
- Confirm the correct KB for Windows 10 Version 1607 and Windows Server 2016 in the MSRC Security Update Guide before patching.
- Identify remaining Windows 10 Version 1607 and Server 2016 systems; check their support status and migrate unsupported systems to supported releases.
- Restrict local logon and standard-user installation rights where possible.
- Monitor for unusual privilege changes and new local administrator accounts.
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
- Microsoft Security Update Guide: CVE-2026-87711 msrc.microsoft.com
- OpenCVE: CVE-2026-87711 app.opencve.io
- Vulners: CVE-2026-87711 (CNA data) vulners.com
- Vulners: Microsoft advisory MS:CVE-2026-87711 vulners.com
- Vulners: CVE-2026-87711 summary 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 2 Nov 2026, 01:33.
Original description (NVD)
Stack-based buffer overflow 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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