CVE-2026-21240 is a high-severity vulnerability affecting Microsoft Windows HTTP.sys. This vulnerability allows an authorized attacker to leverage a time-of-check time-of-use (TOCTOU) race condition to elevate privileges locally. The CVSS score associated with this vulnerability is 7.8, indicating a high level of risk.
This vulnerability poses a significant risk to organizations as it can be exploited by unauthorized local users to gain elevated privileges. As such, it is crucial for security teams to assess their environments for exposure to this vulnerability and take necessary actions to mitigate the risks associated with it. Organizations should prioritize patching immediately.
The vulnerability was published on February 10, 2026, and has been classified as 'analyzed' with high exploitation potential. Organizations should remain vigilant and ensure they are applying the relevant patches to protect their systems.
Given the nature of the vulnerability, it is advisable for organizations to include this patch in their priority cycle to ensure that they mitigate any potential risks associated with this vulnerability.
Vulnerability Details
The official description states that the vulnerability is a time-of-check time-of-use (TOCTOU) race condition in Windows HTTP.sys which allows an authorized attacker to elevate privileges locally. It has been assigned a CVSS version 3.1 score of 7.8, with a high severity classification, indicating the critical nature of this vulnerability.
The affected products include multiple versions of Windows 10 and Windows 11, as well as Windows Server editions. The publication date of the vulnerability is February 10, 2026, and it falls under the CWE-367 classification.
Technical Analysis
The root cause of CVE-2026-21240 is a race condition that occurs in the HTTP.sys component of Windows. This vulnerability can be exploited locally, meaning that an attacker must have access to the system to leverage this vulnerability. The attack complexity is classified as low, and the privileges required for exploitation are also low, with no user interaction necessary.
Exploitation of this vulnerability can lead to high impacts on confidentiality, integrity, and availability, indicating that a successful exploit could allow an attacker to manipulate the system in significant ways.
Risk & Impact Analysis
Risk to organizations includes the potential for unauthorized local users to gain elevated privileges, leading to further exploitation of sensitive information and operational disruption. The blast radius is significant, as multiple Windows and Server versions are affected, broadening the potential impact on diverse environments.
Given the CVSS score and the absence of public exploits, organizations should assess their exposure risk and prioritize remediation efforts. This vulnerability's impact should prompt immediate attention in security patch cycles.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The affected versions include various editions of Windows 10 and Windows 11, as well as Windows Server versions. Specifically, all versions prior to vendor patch are vulnerable.
Mitigation & Remediation
Organizations should prioritize patching immediately to remediate this vulnerability. It is essential to update to the latest versions, specifically ensuring that all affected systems are patched. For those unable to upgrade immediately, temporary workarounds should be considered to limit exposure.
For detailed guidance on penetration testing services, organizations can refer to penetration testing services to assess vulnerabilities effectively.
Detection Guidance
Monitoring for log indicators that reveal unauthorized access attempts or privilege escalation behaviors can help in detecting potential exploitation. Organizations should also look for behavioral anomalies that may indicate attempts to exploit this vulnerability.
AppSecure Threat Intelligence Insight
This vulnerability highlights the ongoing challenges organizations face with race conditions in software. By implementing effective security measures and conducting regular security assessments, teams can better mitigate risks associated with vulnerabilities like CVE-2026-21240.
Security teams should stay informed about patterns and trends in vulnerability exploitation, as well as adopt strategic defensive measures to safeguard their environments. For more insights on vulnerability management, refer to vulnerability management program design and best practices to enhance security posture.
Continuous improvement in security practices is essential to address evolving threats, and organizations are encouraged to engage in penetration testing methodology to identify and remediate potential vulnerabilities proactively.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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