EUVD-2026-43929
GHSA-3gwp-qggg-mg8c
Severity by source
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Local low-privileged attacker (AV:L/PR:L), high complexity due to a use-after-free race (AC:H), full SYSTEM compromise gives C:H/I:H/A:H with no scope change.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Use after free in Windows Kernel allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in the Microsoft Windows Kernel lets an already-authenticated attacker win a use-after-free race (CWE-416) to gain SYSTEM-level control, affecting a broad range of client and server builds from Windows 10 1607 and Windows Server 2012 through Windows 11 26H1 and Windows Server 2025. Microsoft has released a patch and there is no public exploit identified at time of analysis. The moderate 7.0 score reflects high attack complexity (a timing-dependent race) offset by full confidentiality, integrity and availability impact once triggered.
Technical ContextAI
The flaw sits in the Windows Kernel (ntoskrnl / kernel-mode components), the core ring-0 trust boundary that mediates all process, memory and object management on Windows. CWE-416 (Use After Free) means a kernel object is dereferenced after it has been freed, typically because a reference count or object lifetime is mishandled during concurrent operations; an attacker who can reallocate the freed memory with controlled data can corrupt kernel structures and hijack execution or manipulate privilege tokens. The CPE set spans Microsoft client SKUs (Windows 10 1607/1809/21H2/22H2, Windows 11 24H2/25H2/26H1) and server SKUs (Windows Server 2012, 2012 R2, 2016, 2019, 2022, 2025, including Server Core installations), indicating the vulnerable code is in a long-lived, shared kernel path present across more than a decade of releases.
RemediationAI
Patch available per vendor advisory: apply the Microsoft security update for CVE-2026-50397 delivered through the monthly cumulative/quality update for each affected SKU, using the exact patched build listed for your edition at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50397 (the input does not provide a single fixed version string, so consult the advisory for the per-SKU KB and build). Because exploitation requires the attacker to already hold local, low-privileged code execution, effective compensating controls until patching include restricting and monitoring the ability to run untrusted code (application allow-listing / WDAC), enforcing least privilege to shrink the pool of accounts that can stage the race, and prioritizing patch deployment on multi-user and shared hosts (RDS, jump boxes) where untrusted low-privilege users are most likely; note these controls reduce but do not eliminate risk, and Server Core systems must be patched with the corresponding Server Core update.
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Same weakness CWE-416 – Use After Free
View allSame technique Use After Free
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External POC / Exploit Code
Leaving vuln.today