EUVD-2026-43920
GHSA-g784-2pg8-v3q9
Severity by source
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Local privilege escalation needing an existing low-priv account (PR:L) and winning a timing race (AC:H); successful escalation yields full local compromise (C:H/I:H/A:H).
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
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 component of Windows 11 (24H2, 25H2, 26H1) and Windows Server 2025 allows an already-authenticated local attacker to win a race condition and gain higher privileges. The flaw was reported by Microsoft, which has released a patch; there is no public exploit identified at time of analysis and it is not listed in CISA KEV. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the attacker to already have local access with at least low-level authenticated privileges (PR:L) on an affected Windows 11 24H2/25H2/26H1 or Windows Server 2025 system - this is not remotely exploitable (AV:L) and needs no user interaction (UI:N). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 base score is 7.0 (High) with vector AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H - meaning local access and existing low privileges are required, exploitation is of high complexity (winning a race), no user interaction is needed, scope is unchanged, and successful exploitation yields full high impact to confidentiality, integrity, and availability. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who has already obtained a low-privileged local account or code execution on a Windows 11 or Windows Server 2025 host repeatedly triggers the vulnerable Windows Runtime operation while racing a second thread to manipulate the shared resource during the unsynchronized window. On a successful race they escalate to higher (up to SYSTEM-level) privileges, gaining full control of the machine. … |
| Remediation | Patch available per vendor advisory - apply the Microsoft security update for CVE-2026-50403 as documented at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50403, selecting the KB corresponding to your specific Windows 11 (24H2/25H2/26H1) or Windows Server 2025 build (including Server Core). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory all Windows 11 (24H2, 25H2, 26H1) and Windows Server 2025 systems in your environment and assess exposure to locally-authenticated users. …
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External POC / Exploit Code
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