CVE-2026-21237 is a high-severity vulnerability affecting Microsoft Windows Subsystem for Linux. This vulnerability allows concurrent execution using shared resources with improper synchronization, known as a 'race condition'. An authorized attacker can leverage this condition to elevate privileges locally, posing a significant security risk. The CVSS score for this vulnerability is 7, which indicates a high risk level that organizations must address promptly.
Risk to organizations includes unauthorized access and potential data compromise, as attackers may leverage this flaw to gain higher privileges within the affected systems. Given the nature of the vulnerability, organizations should prioritize patching immediately to mitigate this risk.
The vulnerability was published on February 10, 2026, and has been analyzed thoroughly. No public exploit has been confirmed at this time, but the potential impact necessitates immediate attention from security teams.
Organizations using affected versions of Windows should ensure they are included in their patch management processes to address this vulnerability promptly.
Vulnerability Details
The official CVE description highlights a race condition in the Windows Subsystem for Linux that allows privilege escalation. The vulnerability is classified under CWE-362, which pertains to a concurrent execution using shared resource with improper synchronization. The CVSS score of 7 indicates a high severity level due to potential impacts on confidentiality, integrity, and availability.
The affected products include various versions of Windows 10 and Windows 11, as well as Windows Server 2022 and Windows Server 2025. The vulnerability affects all versions prior to the vendor patch, specifically before 10.0.19044.6937 for Windows 10 and various other version endpoints for the remaining systems.
Technical Analysis
The root cause of CVE-2026-21237 is a race condition that occurs when multiple threads access shared resources without proper synchronization. This vulnerability can be exploited locally by an attacker who has some privileges on the system, specifically with low privileges and no user interaction required.
The attack vector is local, meaning the attacker must have access to the target system. The complexity of the attack is considered high, as it requires an understanding of the internal workings of the Windows Subsystem for Linux and precise timing to exploit the race condition effectively.
The potential impact of this vulnerability is severe, with confidentiality, integrity, and availability all rated as high in the CVSS metrics. Successful exploitation could allow the attacker to fully compromise the system, leading to unauthorized access and control.
Risk & Impact Analysis
Organizations are at significant risk due to this vulnerability, particularly those using affected versions of Windows. The potential for local privilege escalation can lead to unauthorized access to sensitive data and system controls, increasing the blast radius of an attack.
Given the high CVSS score and the nature of the vulnerability, organizations should assess their exposure and prioritize remediation efforts. The urgency of addressing this vulnerability is underscored by the potential for exploitation, which could result in significant operational and reputational damage.
Organizations should implement a robust vulnerability management program to ensure timely patching and monitoring of affected systems. The EPSS score of 0.00032 indicates a low probability of exploitation, but the implications of an exploit necessitate proactive measures.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The affected versions include Windows 10 (21H2 and 22H2), Windows 11 (23H2, 24H2, and 25H2), and Windows Server 2022 and 2025. All versions prior to the vendor patch are vulnerable, specifically versions prior to 10.0.19044.6937 for Windows 10 and similarly for other components.
Mitigation & Remediation
To mitigate this vulnerability, organizations should ensure they apply the latest patches provided by Microsoft. The recommended version to upgrade to is 10.0.19044.6937 or later for Windows 10 systems, as well as subsequent updates for Windows 11 and Server versions.
Organizations unable to apply patches immediately should consider implementing configuration hardening measures, such as restricting access to vulnerable systems and monitoring for unusual activity. For more detailed guidance, organizations can refer to the penetration testing services that help identify vulnerabilities in their environments.
Detection Guidance
Organizations should monitor logs for indicators of exploitation attempts related to this vulnerability. Key indicators could include unexpected privilege escalations and unusual access patterns. Behavioral anomalies in the Windows Subsystem for Linux environment should also be noted as potential signs of exploitation.
AppSecure Threat Intelligence Insight
CVE-2026-21237 highlights the ongoing need for vigilance in monitoring and securing local systems, especially those utilizing shared resources. As organizations increasingly adopt complex environments, understanding such vulnerabilities will be crucial for maintaining security posture.
Security teams must prioritize awareness and training related to the exploitation of race conditions, as these types of vulnerabilities can often be overlooked in traditional security assessments. For more information on effective practices, organizations can explore our penetration testing methodology and how it can enhance their security posture.
By understanding the implications of this vulnerability and adopting proactive measures, organizations can significantly reduce their risk exposure and enhance their overall security.
For further insights into emerging vulnerabilities and their mitigation, organizations can refer to our vulnerability management program design guide, which provides comprehensive strategies for managing vulnerabilities effectively.
Lastly, organizations should stay informed about trends in vulnerabilities and exploits by following our blog, where we regularly update on the latest threats and defensive strategies.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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