EUVD-2026-43990
GHSA-mvfj-xq2q-p2rj
Severity by source
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Local-only race condition requiring an authenticated low-privileged foothold (AV:L/PR:L), unreliable timing window (AC:H), no user interaction, yielding full-impact privilege escalation (C/I/A:H).
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 component (Windows 10 1607 through Windows 11 26H1, and Windows Server 2016 through 2025) allows an authorized low-privileged attacker to win a race condition on an improperly synchronized shared resource and gain higher privileges. Exploitation is local-only and high-complexity because it depends on reliably hitting a narrow timing window, and no public exploit has been identified at time of analysis. A vendor patch is available via Microsoft's MSRC update guide.
Technical ContextAI
The flaw resides in the Windows App Store servicing/packaging component that ships across the modern Windows client and server line. Per the CPE data it affects Windows 10 (1607, 1809, 21H2, 22H2), Windows 11 (24H2, 25H2, 26H1), and Windows Server 2016, 2019, 2022, and 2025 including Server Core installations. The root cause is CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization, i.e. a race condition): two or more execution flows access a shared resource without adequate locking, creating a time-of-check-to-time-of-use style window. An attacker who can interleave operations against that resource at the right moment can subvert a privileged action the component performs, causing it to operate on attacker-controlled data or state and thereby cross a privilege boundary.
RemediationAI
Patch available per vendor advisory: apply the Microsoft security update referenced at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-49784, selecting the KB that matches your specific OS build (the update guide lists per-version fixed builds not included in this dataset). Because exploitation requires local low-privileged access and there is no documented configuration workaround, the primary compensating control until patching is to limit who can execute code on affected hosts - restrict interactive and remote-desktop logon rights on shared, multi-user, and server systems, and enforce least privilege so untrusted accounts cannot run arbitrary local processes. Given AC:H, standard endpoint monitoring for repeated crashes or anomalous App Store/packaging service activity can also help detect exploitation attempts; there is no port- or feature-level toggle to disable, so patching is the definitive fix.
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Same weakness CWE-362 – Race Condition
View allSame technique Race Condition
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External POC / Exploit Code
Leaving vuln.today