Microsoft Windows DWM Core Library: Out-of-bounds read in local privilege escalation
Summary
The Windows Desktop Window Manager (DWM) Core Library contains an out-of-bounds read (CWE-125). A local user with existing low-privilege access can exploit it to elevate privileges to a higher level, with high impact on confidentiality, integrity and availability. The attack is not remote. It matters most after another compromise, such as phishing or malware, and on multi-user systems such as terminal or RDS servers.
Affected
- Windows 10 Version 1809 and Windows Server 2019 (incl. Server Core): 10.0.17763.0 to before 10.0.17763.9376
- Windows 10 Version 21H2: 10.0.19044.0 to before 10.0.19044.7807
- Windows 10 Version 22H2: range listed by the CNA is inconsistent, exact build unknown
- 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 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 (incl. Server Core): 10.0.26100.0 to before 10.0.26100.33650
- Note: the NVD CPE lists only Windows 10 1809; the CNA record lists the products above. Verify on MSRC.
Fixed in
- Windows 10 1809 and Server 2019: 10.0.17763.9376 or later
- Windows 10 21H2: 10.0.19044.7807 or later
- Windows 10 22H2: Unknown.
- Windows 11 23H2: 10.0.22631.7652 or later
- Windows 11 24H2: 10.0.26100.9711 or later
- Windows 11 25H2: 10.0.26200.9711 or later
- Windows 11 26H2: 10.0.26300.9711 or later
- Windows Server 2022: 10.0.20348.5761 or later
- Windows Server 2025: 10.0.26100.33650 or later
- The KB numbers are unknown and must be confirmed on MSRC.
Workaround
None documented.
Exploitation
- No public proof of concept known.
- No evidence of exploitation in the wild found. Not listed in CISA KEV according to VulDB.
- CISA SSVC: exploitation none, automatable no, technical impact total.
Our recommendation
- Install the October 2026 security update on all affected Windows 10, Windows 11 and Windows Server systems. Confirm the exact build and KB number on MSRC first.
- Prioritise multi-user systems, RDS and terminal servers, shared workstations and older Windows 10 1809 hosts. Check their support status and whether Extended Security Updates apply.
- Limit local logon rights and remove unnecessary local accounts.
- Monitor MSRC and CISA for changes in exploitation status.
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows DWM Core Library
- 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 (MSRC) msrc.microsoft.com
- VulDB entry 419508 vuldb.com
- Vulners CVE record (CNA affected ranges) vulners.com
- OpenCVE CVE-2026-88189 app.opencve.io
- Strix.ai CVE-2026-88189 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 2 Nov 2026, 01:05.
Original description (NVD)
Out-of-bounds read in Windows DWM Core Library 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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