Microsoft Windows: Use-after-free in Program Compatibility Assistant Service
Summary
A use-after-free vulnerability (CWE-416) in the Windows Program Compatibility Assistant Service allows an authorized local user with low privileges to elevate privileges. The attack requires local access and has high complexity. Microsoft fixed the issue in the October 13, 2026 updates, and no public exploit or active exploitation is known.
Affected
- Windows 11 version 23H2: builds 10.0.22631.0 to before 10.0.22631.7652
- Windows 11 version 24H2: builds 10.0.26100.0 to before 10.0.26100.9711
- Windows 11 version 25H2: builds 10.0.26200.0 to before 10.0.26200.9711
- Windows 11 version 26H1: builds 10.0.28000.0 to before 10.0.28000.3231
- Windows 11 version 26H2: builds 10.0.26300.0 to before 10.0.26300.9711
- Windows Server 2025 (including Server Core): builds 10.0.26100.0 to before 10.0.26100.33650
Fixed in
- Windows 11 version 23H2: build 10.0.22631.7652 or later (October 13, 2026 cumulative update, KB5126653)
- Windows 11 versions 24H2, 25H2, 26H1, 26H2 and Windows Server 2025: October 13, 2026 security updates (builds listed above)
- Windows 11 23H2 Home and Pro are out of service and receive no fix; an upgrade is required.
Workaround
Unknown.
Exploitation
- Publicly disclosed: No (per Microsoft)
- Exploitation: none reported (CISA SSVC: exploitation none, automatable no)
- Not listed in the CISA KEV catalog
Our recommendation
- Install the October 13, 2026 cumulative update on all affected Windows 11 and Windows Server 2025 systems through Windows Update or your patch management tool.
- Prioritise shared computers, terminal/RDS servers and jump hosts.
- Upgrade or retire Windows 11 23H2 Home and Pro devices, as they no longer receive security updates.
- Check the MSRC advisory for updated mitigation information.
Information from Microsoft (Patch Tuesday October 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft MSRC advisory CVE-2026-72934 msrc.microsoft.com
- NVD mirror with fixed-version list (Vulners) vulners.com
- OpenCVE CVE-2026-72934 (KEV, SSVC, EPSS) app.opencve.io
- Windows Update announcement x.com
- NinjaOne KB5126653 summary www.ninjaone.com
- Windows 11 version history (Wikipedia) en.wikipedia.org
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 4 Nov 2026, 08:50.
Original description (NVD)
Use after free in Windows Program Compatibility Assistant 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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