Windows Update Delivery Optimization: Use after free enables privilege escalation
Summary
A use-after-free flaw in the Windows Update Delivery Optimization component allows a local, authenticated user to elevate privileges. The attack complexity is high and no network access is needed, so the main risk comes from standard users, compromised accounts or malicious insiders on systems with local logons. The vendor rates the impact as total on confidentiality, integrity and availability.
Affected
- Windows 10 Version 1809 (Server 2019 line): 10.0.17763.0 to below 10.0.17763.9376
- Windows 10 Version 21H2: 10.0.19044.0 to below 10.0.19044.7807
- Windows 10 Version 22H2: 10.0.19045.0 to below 10.0.19045.7807
- Windows 11 Version 23H2: 10.0.22631.0 to below 10.0.22631.7652
- Windows 11 Version 24H2: 10.0.26100.0 to below 10.0.26100.9711
- Windows 11 Version 25H2: 10.0.26200.0 to below 10.0.26200.9711
- Windows 11 Version 26H1: 10.0.28000.0 to below 10.0.28000.3231
- Windows 11 Version 26H2: 10.0.26300.0 to below 10.0.26300.9711
- Windows Server 2019 (including Server Core): 10.0.17763.0 to below 10.0.17763.9376
- Windows Server 2022: 10.0.20348.0 to below 10.0.20348.5761
- Windows Server 2025 (including Server Core): 10.0.26100.0 to below 10.0.26100.33650
Fixed in
- Windows 10 1809 and Windows Server 2019: 10.0.17763.9376 (KB5126651)
- Windows 10 21H2: 10.0.19044.7807
- Windows 10 22H2: 10.0.19045.7807 (KB5126657)
- Windows 11 23H2: 10.0.22631.7652 (KB5126653)
- 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 (KB5126655)
- Windows Server 2025: 10.0.26100.33650 (KB5126646)
Workaround
Unknown.
Exploitation
- CISA SSVC assessment: exploitation none, not automatable, total technical impact
- No public proof of concept or evidence of active exploitation found at the time of research
- EPSS about 0.0025 (low predicted exploitation probability)
Our recommendation
- Install the October 2026 Windows cumulative update on all affected systems, starting with Windows 10 1809 and Server 2019 systems
- Check whether any Windows 10 1809 systems outside Enterprise LTSC or Server 2019 still run, as they may no longer receive fixes
- Limit local logon rights and restrict local accounts on shared workstations, terminal servers and file or print servers
- Monitor for unusual privilege changes and raise the priority if public exploit code or active exploitation is reported
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows Update Delivery Optimization
- 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, KB5126657, KB5126655, KB5126653, KB5127648, KB5126646
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide msrc.microsoft.com
- NVD mirror (Vulners) vulners.com
- CNA record mirror (Vulners) vulners.com
- Positive Technologies / KB mapping (Vulners) vulners.com
- Strix.ai CVE page www.strix.ai
- Windowsforum analysis windowsforum.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, 09:42.
Original description (NVD)
Use after free in Windows Update Delivery Optimization 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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