EUVD-2026-43895
GHSA-mfrp-f2w3-cjvx
Severity by source
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Local access with an existing low-privileged account (AV:L/PR:L), a non-deterministic race window drives AC:H, and privilege elevation yields full C:H/I:H/A:H with 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) component of Windows 11 (24H2, 25H2, 26H1) and Windows Server 2025 allows an authenticated local attacker to win a race condition and gain higher privileges. The flaw stems from improper synchronization of a shared resource (CWE-362); successful exploitation yields high confidentiality, integrity, and availability impact. No public exploit is identified at time of analysis, and it is not listed in CISA KEV; Microsoft has released a patch.
Technical ContextAI
Windows Runtime (WinRT) is the object-oriented API layer that underpins modern Windows applications and system services across the OS. The root cause is CWE-362, a race condition arising from concurrent execution over a shared resource without proper synchronization: two or more threads access the same object during a narrow timing window, letting an attacker manipulate state between a check and its use (TOCTOU-style). Per the CPE data the flaw is present in the application layer of Windows 11 Version 24H2, 25H2, and 26H1, plus Windows Server 2025 including the Server Core installation, indicating a shared code path in the current Windows servicing branch rather than a legacy-only defect.
RemediationAI
Patch available per vendor advisory - apply the Microsoft security update for CVE-2026-50345 to all affected Windows 11 24H2/25H2/26H1 and Windows Server 2025 (including Server Core) systems via the monthly cumulative update; the fixed build numbers are listed in the MSRC guidance at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50345. No standalone workaround is documented in the provided data, and because the vulnerability requires prior local low-privileged access, the practical compensating controls until patching are to reduce the population of local users who could stage the attack: enforce least privilege, restrict interactive and remote-desktop logon rights on servers, and prioritize patching multi-user and shared hosts (RDS/session hosts) where untrusted low-privileged accounts run code, since those most directly satisfy the PR:L precondition.
More in Windows Server 2025
View allWindows Internet Shortcut Files (.url) contain an external control vulnerability (CVE-2025-33053, CVSS 8.8) that enables
Windows SMB contains an improper access control vulnerability (CVE-2025-33073, CVSS 8.8) enabling authenticated attacker
Active Directory Domain Services contains an elevation of privilege vulnerability that allows authenticated domain users
Microsoft Scripting Engine contains a type confusion vulnerability allowing unauthorized remote code execution over the
Windows Task Scheduler Elevation of Privilege Vulnerability. Rated high severity (CVSS 8.8), this vulnerability is low a
Remote code execution in Windows IKE Extension (Internet Key Exchange) via double free memory corruption allows unauthen
Symlink following (CWE-59) in the Windows Update Stack enables a locally authenticated attacker with standard user privi
Local privilege escalation in Microsoft Active Directory Federation Services (AD FS) lets an already-authenticated low-p
A security feature bypass in Microsoft Management Console (MMC) allows attackers to evade security warnings and execute
Privilege escalation in the Windows Ancillary Function Driver for WinSock (afd.sys) allows a locally authenticated attac
Windows CLFS Driver contains an input validation flaw enabling local privilege escalation, yet another CLFS kernel vulne
Windows Ancillary Function Driver for WinSock contains a heap-based buffer overflow enabling local privilege escalation
Same weakness CWE-362 – Race Condition
View allSame technique Information Disclosure
View allShare
External POC / Exploit Code
Leaving vuln.today