Microsoft Windows 11 26H1: Elevation of privilege in Windows Kernel
Summary
An untrusted pointer dereference in the Windows kernel of Windows 11 version 26H1 allows an attacker to elevate privileges. Exploitation requires physical access to the device and no user interaction or prior privileges. A successful attack can lead to a full compromise of confidentiality, integrity and availability on the affected system.
Affected
- Microsoft Windows 11 version 26H1 (ARM64-based and x64-based systems)
- Versions 10.0.28000.0 before 10.0.28000.3231
Fixed in
- Fixed in cumulative update KB5127646 (OS Build 28000.3231) and later 26H1 builds, according to Microsoft's advisory
- Later builds 28000.3237 and 28000.3365 are reported to exceed the fixed version; verify their KB contents before relying on them
Workaround
- No workaround known. Apply the security update.
Exploitation
- No known exploitation in the wild. CISA KEV: not listed (per mirrored data, not verified directly).
- No public proof of concept found.
- CISA SSVC: Exploitation none, Automatable no, Technical Impact total.
Our recommendation
- Apply KB5127646 or a later 26H1 update to affected devices.
- Note the known issue in KB5127646: Remote Desktop connections may fail for non-admin users with error 0xC000000D; check RDP access after patching and install the update released on or after October 27, 2026 (KB5127653) if needed.
- Confirm whether your clients run Windows 11 26H1; most fleets run other branches.
- Enforce BitLocker, a strong boot PIN and session locking to reduce the risk of physical access attacks, with priority on mobile and shared devices.
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows Kernel
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Windows
- Updates (KB)
- KB5127646
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-103578 msrc.microsoft.com
- Microsoft Support: KB5127646 Windows 11 26H1 security update support.microsoft.com
- Vulners CVE list record CVE-2026-103578 vulners.com
- CVE threatint mirror CVE-2026-103578 cve.threatint.com
- Neowin: Windows 11 KB5127648 and KB5127646 updates www.neowin.net
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, 22:11.
Original description (NVD)
Untrusted pointer dereference in Windows Kernel allows an unauthorized attacker to elevate privileges with a physical attack.
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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