Windows: Use-after-free in Program Compatibility Assistant Service
Summary
A use-after-free vulnerability in the Windows Program Compatibility Assistant (PCA) Service affects supported Windows 10, Windows 11 and Windows Server systems, including Windows 10 Version 1607 and Windows Server 2016. An authorized local user with low privileges can exploit it to elevate privileges. Exploitation requires local access and a high-complexity attack, so the flaw is not directly reachable from the network.
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 (vendor range inconsistent, verify on MSRC)
- 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 2016 and Server Core (builds below 10.0.14393.9612)
- Windows Server 2019 and Server Core (builds below 10.0.17763.9376)
- Windows Server 2022 (builds below 10.0.20348.5761)
Fixed in
- Windows 10 Version 1607 / Windows Server 2016: build 10.0.14393.9612 (October 2026 update, reportedly KB5126868, confirm on MSRC)
- Other listed versions: fixed in the October 2026 security update per the builds above
- Windows 10 Version 22H2: fixed build unclear in the source data, confirm on MSRC
Workaround
Unknown.
Exploitation
- No public exploit or in-the-wild exploitation found at the time of research.
- Not listed in the CISA KEV catalog.
- CISA SSVC: exploitation none, automatable no, technical impact total.
- EPSS score 0.0027 (low probability of exploitation).
Our recommendation
- Install the October 2026 security update on all supported Windows systems.
- Check whether Windows 10 Version 1607 and Windows Server 2016 hosts still receive updates, and plan upgrades for unsupported systems.
- Prioritize shared workstations, terminal or RDS servers and kiosks, where local users could escalate privileges.
- Confirm fixed builds and KB numbers on the MSRC advisory before rollout.
- Monitor for a public PoC or KEV addition.
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows Program Compatibility Assistant 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)
- KB5126651, KB5126655, KB5126657, KB5126646, KB5127648, KB5126653
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-69596 msrc.microsoft.com
- Tenable: Windows 10 1607 / Server 2016 October 2026 update (KB5126868) www.tenable.com
- Vulners NVD record CVE-2026-69596 (EPSS) vulners.com
- OpenCVE: CVE-2026-69596 (KEV and SSVC status) app.opencve.io
- Strix: CVE-2026-69596 CNA data 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 4 Nov 2026, 09:37.
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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