EUVD-2026-44110
GHSA-f892-ww2f-8858
Severity by source
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Local authenticated user (AV:L/PR:L) must win a narrow timing window (AC:H) with no interaction; successful escalation yields full host C/I/A impact within 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 Windows Runtime allows an authorized attacker to elevate privileges locally.
AnalysisAI
Local privilege escalation in the Windows Runtime (WinRT) affects current Microsoft platforms including Windows 11 24H2, 25H2, 26H1, and Windows Server 2025, where a race condition (CWE-362) in the handling of a shared resource lets an already-authenticated local user win a timing window to gain higher privileges. Microsoft has released a patch, and there is no public exploit identified at time of analysis. With a CVSS 7.0 (AV:L/AC:H/PR:L) the flaw requires local access and precise timing, making it a plausible second-stage escalation rather than an initial entry point.
Technical ContextAI
The Windows Runtime (WinRT) is the object-oriented API surface underpinning modern Windows apps and many OS components across Windows 11 and Windows Server 2025. The root cause is CWE-362, concurrent execution using a shared resource with improper synchronization - a classic race condition. When two or more threads/processes access a shared object without adequate locking, an attacker who can run code on the box can interleave operations (e.g., time-of-check to time-of-use) to manipulate the shared resource in a privileged context, causing the runtime to act on attacker-controlled state. The CPE data scopes the affected surface to Microsoft's latest client and server builds (windows_11_version_24h2/25h2/26h1, windows_server_2025 including Server Core), indicating the vulnerable WinRT component ships in the base OS rather than an optional feature.
RemediationAI
Patch available per vendor advisory - apply the Microsoft security update for CVE-2026-50503 via the standard Windows Update / WSUS / Microsoft Update Catalog channels for each affected platform (Windows 11 24H2/25H2/26H1 and Windows Server 2025 including Server Core), referencing https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50503 for the exact KB and fixed build number. Because exploitation requires an authenticated local user, interim compensating controls until patching completes include restricting interactive and remote-desktop logon rights to trusted administrators, limiting local code execution by non-admin users through application control (WDAC/AppLocker), and prioritizing multi-user or shared hosts (RDS, jump servers) where untrusted local principals are most likely; note these controls reduce but do not eliminate exposure since any legitimate local account remains a potential vector, and they may impact user workflows on shared systems. No standalone configuration workaround was published, 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