Windows 11 23H2: Local privilege escalation via use-after-free in Program Compatibility Assistant
Summary
A use-after-free vulnerability in the Windows Program Compatibility Assistant Service allows a local, authorized attacker to elevate privileges. The attacker needs low privileges and a foothold on the system, and the attack complexity is high. Successful exploitation can give high impact on confidentiality, integrity and availability, which makes shared and terminal servers especially exposed.
Affected
- Windows 11 version 23H2: 10.0.22631.0 to before 10.0.22631.7652
- Windows 11 version 24H2: 10.0.26100.0 to before 10.0.26100.9711
- Windows 11 version 25H2: 10.0.26200.0 to before 10.0.26200.9711
- Windows 11 version 26H1: 10.0.28000.0 to before 10.0.28000.3231
- Windows 11 version 26H2: 10.0.26300.0 to before 10.0.26300.9711
- Windows Server 2025 (including Server Core installation): 10.0.26100.0 to before 10.0.26100.33650
Fixed in
- Windows 11 23H2: KB5126653 (released October 13, 2026), build 10.0.22631.7652 or later
- Windows 11 26H1: KB5127646, build 10.0.28000.3231 or later
- Windows 11 24H2, 25H2 and 26H2: KB5127648, builds 10.0.26100.9711, 10.0.26200.9711 and 10.0.26300.9711 or later
- Windows Server 2025: build 10.0.26100.33650 or later (KB number not confirmed in the sources)
Workaround
Unknown. No vendor workaround was found. Installing the update is the fix. Until patched, limit local interactive logons and restrict who can run code on shared and terminal servers.
Exploitation
- Not known to be exploited; MSRC marks exploit maturity as Unproven
- No public exploit or proof of concept known
- EPSS score 0.0027 (very low)
- CISA SSVC: exploitation none, automatable no, technical impact total
- CISA KEV status not verified
Our recommendation
- Install KB5126653 on Windows 11 23H2 devices in the October 2026 update cycle, prioritising terminal servers and admin workstations.
- Verify that all 23H2 devices are at build 10.0.22631.7652 or later.
- Install the fixes for the other affected builds listed above.
- Plan the move away from 23H2 before end of servicing (Enterprise and Education editions, November 2026).
- Monitor MSRC and CISA KEV for changes in exploitation status.
Information from Microsoft (Patch Tuesday October 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-69743 msrc.microsoft.com
- Microsoft Security Update Guide (en-US) msrc.microsoft.com
- NinjaOne: KB5126653 www.ninjaone.com
- Windows Update announcement on X x.com
- Microsoft message center MC1506288 mc.merill.net
- BleepingComputer: KB5127648 and KB5126653 released www.bleepingcomputer.com
- OpenCVE: CVE-2026-69743 app.opencve.io
- Vulners NVD: CVE-2026-69743 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 4 Nov 2026, 09:35.
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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