Microsoft Windows: Use after free in Application Compatibility Cache
Summary
A use-after-free flaw in the Windows Application Compatibility Cache allows an authorized local attacker to elevate privileges. An attacker who already runs code as a low-privileged user could gain SYSTEM rights. The attack complexity is high, and no user interaction is required. The vulnerability is a post-foothold risk, not an entry point from the internet.
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 2022 (10.0.20348.0 to before 10.0.20348.5761)
- Windows Server 2025 and Server Core installation (10.0.26100.0 to before 10.0.26100.33650)
Fixed in
- Windows 11 23H2: 10.0.22631.7652
- Windows 11 24H2: 10.0.26100.9711
- Windows 11 25H2: 10.0.26200.9711
- Windows 11 26H1: 10.0.28000.3231
- Windows 11 26H2: 10.0.26300.9711
- Windows Server 2022: 10.0.20348.5761
- Windows Server 2025: 10.0.26100.33650
- Fix released with the October 13, 2026 security update. Knowledge base numbers: unverified, check the MSRC advisory.
Workaround
Unknown. No workaround or mitigation was found in the consulted sources. Patching is the only documented remedy.
Exploitation
- Microsoft reports: publicly disclosed No, exploited No.
- CISA SSVC (ADP): exploitation none, automatable no, technical impact total.
- No CISA KEV listing found; no public proof of concept found in the sources consulted.
Our recommendation
- Install the October 13, 2026 cumulative update on all affected Windows 11 and Windows Server systems as part of the normal monthly cycle.
- Prioritize multi-user servers, RDS/terminal servers and shared workstations.
- If a user-level compromise is known or suspected, patch these systems first.
- Monitor endpoints for unusual privilege escalation and suspicious processes running as SYSTEM.
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows Application Compatibility Cache
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation more likely
- Product family
- Windows
- Updates (KB)
- KB5127648, KB5126655, KB5126646, KB5126653, KB5127646
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- MSRC Security Update Guide advisory msrc.microsoft.com
- MSRC exploitability details (en-US) msrc.microsoft.com
- NVD mirror (Vulners) vulners.com
- CNA version data (Strix) www.strix.ai
- OpenCVE (ADP SSVC data) app.opencve.io
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, 08:51.
Original description (NVD)
Use after free in Windows Application Compatibility Cache 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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