EUVD-2026-43840
GHSA-7c82-69f2-m6j7
Severity by source
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Local-only access with a pre-existing low-privileged account (AV:L, PR:L); winning the race is timing-dependent (AC:H); successful EoP yields full local C/I/A impact within an unchanged scope.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
2DescriptionCVE.org
Concurrent execution using shared resource with improper synchronization ('race condition') in Microsoft Windows App Store allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in the Microsoft Windows App Store (AppX/package deployment component) allows an authorized, low-privileged user to win a race condition and gain higher privileges on affected Windows client and server builds spanning Windows 10 1607 through Windows 11 26H1 and Windows Server 2016 through 2025. Exploitation requires local access and already-held low privileges, and the high attack complexity reflects the timing precision needed to win the race. There is no public exploit identified at time of analysis and it is not listed in CISA KEV, but Microsoft has released a patch.
Technical ContextAI
The flaw is a CWE-362 race condition (concurrent execution using a shared resource with improper synchronization) in the Windows App Store / AppX packaging and deployment subsystem, the component responsible for installing, updating, and running Store/MSIX applications. Because this deployment machinery runs with elevated system rights while acting on behalf of, or on resources reachable by, a normal user, a time-of-check-to-time-of-use (TOCTOU) style window can let a low-privileged process substitute or manipulate a shared resource between validation and use. The CPE set (cpe:2.3:a:microsoft:windows_10_version_1607 through windows_11_version_26h1, plus windows_server_2016/2019 and, per tags, 2022/2025) identifies the affected OS builds; the shared AppX servicing stack is present across all supported Windows editions, which is why the exposure is so broad.
RemediationAI
Apply the Microsoft security update for CVE-2026-50356 (Patch available per vendor advisory) to all affected Windows 10, Windows 11, and Windows Server systems; the exact patched build for each edition is listed at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50356. Because exploitation requires an authenticated local user, primary compensating controls until patching completes are to restrict interactive and local logon rights to trusted accounts, remove unnecessary local users, and apply least-privilege so fewer principals meet the PR:L prerequisite; on servers, prioritize multi-user and RDS/jump hosts where untrusted users can execute code. As a deeper (higher-friction) mitigation you can restrict non-admin AppX/MSIX installation and sideloading via policy, though this may break legitimate Store app deployment and self-service installs, so validate against your application delivery needs before enforcing.
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Same weakness CWE-362 – Race Condition
View allSame technique Information Disclosure
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External POC / Exploit Code
Leaving vuln.today