CVE-2026-50345 Overview
CVE-2026-50345 is a race condition vulnerability in the Windows Runtime component affecting Microsoft Windows 11 and Windows Server 2025. The flaw stems from concurrent execution using a shared resource with improper synchronization [CWE-362]. An authenticated local attacker who wins the race can elevate privileges on the affected host. Microsoft assigned this issue a CVSS 3.1 base score of 7.0 and rated it HIGH severity. The Exploit Prediction Scoring System (EPSS) currently rates the probability of exploitation at 0.193%.
Critical Impact
Successful exploitation grants an authorized local attacker elevated privileges, enabling full compromise of confidentiality, integrity, and availability on the target system.
Affected Products
- Microsoft Windows 11 24H2 (x64 and ARM64)
- Microsoft Windows 11 25H2 (x64 and ARM64)
- Microsoft Windows 11 26H1 (x64 and ARM64)
- Microsoft Windows Server 2025
Discovery Timeline
- 2026-07-14 - CVE-2026-50345 published to NVD
- 2026-07-20 - Last updated in NVD database
Technical Details for CVE-2026-50345
Vulnerability Analysis
The vulnerability resides in the Windows Runtime (WinRT) subsystem, which brokers activation and inter-process operations for modern Windows applications. Windows Runtime coordinates operations across multiple threads and processes, and this coordination relies on synchronization primitives to protect shared state. When those primitives fail to enforce mutual exclusion, two concurrent operations can access the same resource in an unintended interleaving. An attacker who reliably triggers this interleaving can manipulate objects or handles between a validation check and their subsequent use, corrupting state that the runtime later trusts.
Root Cause
The root cause is a race condition [CWE-362] in Windows Runtime code paths that share a resource without adequate locking or atomicity guarantees. The high attack complexity reflected in the CVSS vector indicates that exploitation depends on precise timing windows and specific runtime conditions. Once the race is won, the resulting state confusion allows an attacker holding low privileges to influence operations performed in a higher-privileged context.
Attack Vector
Exploitation requires local access and valid low-privileged credentials on the target system. No user interaction is required. An attacker would run a specifically crafted program that repeatedly invokes the vulnerable Windows Runtime code path while a second thread or process races against the security-sensitive operation. Successful exploitation yields SYSTEM-level or equivalent elevated rights, enabling code execution, credential theft, and persistence.
No public proof-of-concept exploit is available, and Microsoft has not observed active exploitation. Technical specifics are limited to the vendor advisory: Microsoft CVE-2026-50345 Update.
Detection Methods for CVE-2026-50345
Indicators of Compromise
- Unexpected child processes spawned by Windows Runtime broker processes such as RuntimeBroker.exe or dllhost.exe running with elevated integrity levels.
- Repeated, high-frequency invocations of the same WinRT activation API from a single low-privileged process, consistent with race-window brute forcing.
- New services, scheduled tasks, or accounts created shortly after suspicious WinRT activity by a non-administrative user.
Detection Strategies
- Hunt for local privilege transitions where a process launched by a standard user account subsequently executes code at SYSTEM or high integrity without a legitimate elevation event.
- Correlate process creation telemetry with token elevation events (Windows Event ID 4672) originating from non-administrative sessions.
- Baseline normal WinRT broker behavior and alert on statistical outliers in call frequency or thread creation counts.
Monitoring Recommendations
- Enable Microsoft-Windows-Kernel-Process and Sysmon Event ID 1 logging to capture full process ancestry for elevation attempts.
- Forward endpoint telemetry to a centralized analytics platform to correlate short-lived race attempts across hosts.
- Monitor the Microsoft Security Response Center advisory for updated detection guidance and patch supersedence information.
How to Mitigate CVE-2026-50345
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft CVE-2026-50345 Update advisory to all affected Windows 11 and Windows Server 2025 systems.
- Prioritize patching multi-user systems, jump hosts, and terminal servers where local low-privileged access is broadly available.
- Audit local account membership and remove unnecessary interactive logon rights to reduce the pool of potential attackers.
Patch Information
Microsoft has released security updates for Windows 11 24H2, 25H2, 26H1, and Windows Server 2025. Consult the Microsoft Security Response Center for the specific KB article and cumulative update mapped to each build. Deploy through Windows Update, WSUS, or your enterprise patch management tool.
Workarounds
- No official workaround has been published by Microsoft; patching is the required remediation.
- Restrict local logon and Remote Desktop access to trusted administrators where operationally feasible.
- Enforce application allowlisting to block execution of unsigned or unknown binaries that could deliver a race condition exploit.
# Verify installed cumulative update on an affected host
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 10
# Query Windows build to confirm patch applicability
[System.Environment]::OSVersion.Version
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
