CVE-2026-26167: Windows Push Notifications Race Condition

CVE-2026-26167 Overview

CVE-2026-26167 is a race condition vulnerability in Windows Push Notifications that allows an authorized local attacker to elevate privileges. The vulnerability stems from concurrent execution using a shared resource with improper synchronization (CWE-362), enabling attackers with limited access to gain elevated privileges on affected Windows systems.

Critical Impact

An authenticated attacker can exploit this race condition to escalate privileges locally, potentially gaining SYSTEM-level access and compromising the entire host.

Affected Products

• Windows Push Notifications service
• Windows operating systems with Push Notifications enabled

Discovery Timeline

• April 14, 2026 - CVE-2026-26167 published to NVD
• April 14, 2026 - Last updated in NVD database

Technical Details for CVE-2026-26167

Vulnerability Analysis

This vulnerability exists within the Windows Push Notifications service due to improper synchronization when handling shared resources during concurrent execution. The race condition occurs when multiple threads or processes access shared memory or system objects without adequate locking mechanisms, creating a window of opportunity for exploitation.

When the Push Notifications service processes certain operations, an authenticated local attacker can manipulate the timing of concurrent operations to corrupt or hijack the execution flow. Successful exploitation allows the attacker to execute code with elevated privileges, potentially achieving SYSTEM-level access on the compromised host.

The scope change indicated in this vulnerability means that exploitation can impact resources beyond the vulnerable component itself, allowing an attacker to affect the confidentiality, integrity, and availability of the broader system.

Root Cause

The root cause is a Time-of-Check to Time-of-Use (TOCTOU) vulnerability pattern within the Windows Push Notifications service. The service fails to properly synchronize access to shared resources, allowing an attacker to exploit the window between security validation and resource utilization. This improper synchronization mechanism enables an authenticated local attacker to manipulate the state of shared objects between the time they are checked and the time they are used.

Attack Vector

The attack requires local access and low-privilege authentication on the target system. An attacker must:

1. Gain initial access to the Windows system with standard user privileges
2. Identify the timing window in the Push Notifications service's shared resource handling
3. Create competing threads or processes that race to manipulate the shared resource
4. Win the race condition to hijack the privileged execution context
5. Execute arbitrary code with elevated (potentially SYSTEM) privileges

The exploitation does not require user interaction, making it particularly dangerous in environments where attackers have already established a foothold through other means.

Detection Methods for CVE-2026-26167

Indicators of Compromise

• Unusual activity or crashes in the Windows Push Notifications service (WpnService)
• Unexpected privilege escalation events in Windows Security logs
• Multiple rapid service restarts or thread creation patterns in the Push Notifications service
• Anomalous process spawning with elevated privileges originating from notification-related components

Detection Strategies

• Monitor Windows Event Logs for Security Event ID 4688 (Process Creation) with elevated token types
• Implement endpoint detection rules for unusual thread creation patterns in WpnService.dll or related Push Notification components
• Deploy behavioral analytics to detect rapid, repetitive operations targeting the Push Notifications service
• Configure SentinelOne agents to detect privilege escalation attempts through race condition exploitation patterns

Monitoring Recommendations

• Enable Windows Process Auditing to track process creation and privilege changes
• Configure real-time monitoring of the Windows Push Notifications service for stability issues
• Implement SentinelOne's Behavioral AI to detect exploitation attempts targeting local privilege escalation
• Establish baseline activity patterns for the Push Notifications service to identify anomalies

How to Mitigate CVE-2026-26167

Immediate Actions Required

• Apply the latest Windows security updates from Microsoft as soon as they become available
• Review systems for signs of exploitation using the detection methods outlined above
• Restrict local access to critical systems to minimize the attack surface
• Implement the principle of least privilege for user accounts across the environment

Patch Information

Microsoft has released a security update to address this vulnerability. Administrators should consult the Microsoft CVE-2026-26167 Advisory for specific patch information and deployment guidance. Apply the relevant security update through Windows Update, Windows Server Update Services (WSUS), or manual deployment as appropriate for your environment.

Workarounds

• If immediate patching is not possible, consider temporarily disabling the Windows Push Notifications service on critical systems where push notifications are not essential
• Implement application whitelisting to prevent unauthorized code execution
• Restrict local logon rights on sensitive systems to reduce the pool of potential attackers
• Enable Credential Guard and other Windows security features to limit the impact of privilege escalation

# Temporarily disable Windows Push Notifications service (if not required)
sc config WpnService start= disabled
sc stop WpnService

# Re-enable after patching
sc config WpnService start= auto
sc start WpnService