CVE-2026-21236 is a high-severity vulnerability identified in the Microsoft Windows Ancillary Function Driver for WinSock. This vulnerability allows an authorized attacker to execute a heap-based buffer overflow, enabling the attacker to elevate privileges locally. With a CVSS score of 7.8, this vulnerability poses a significant risk to systems running affected Microsoft products.
The risk to organizations includes potential unauthorized access to sensitive information and control over the affected systems. The vulnerability was published on February 10, 2026, and organizations are urged to take immediate action to patch their systems.
Currently, there is no known public exploit for CVE-2026-21236, but the potential for exploitation remains high. Organizations should prioritize patching immediately to mitigate any risks associated with this vulnerability.
As this vulnerability could lead to significant impacts on confidentiality, integrity, and availability, it is crucial for organizations using affected Microsoft products to schedule remediation in their patch cycle.
Vulnerability Details
The vulnerability is characterized by a heap-based buffer overflow in the Windows Ancillary Function Driver for WinSock. It has a CVSS score of 7.8, indicating high severity, and is classified under CWE-122 and CWE-787. The affected products include various versions of Windows 10 and Windows Server, specifically those prior to their respective vendor patches.
Technical Analysis
The root cause of CVE-2026-21236 is a heap-based buffer overflow that occurs due to improper handling of memory allocation in the Windows Ancillary Function Driver. The attack vector is local, and the attack complexity is low, requiring only low privileges with no user interaction needed. The vulnerability impacts confidentiality, integrity, and availability.
Risk & Impact Analysis
Real-world deployment risk is significantly high, as successful exploitation could allow attackers to gain elevated privileges, leading to unauthorized access to sensitive data and system control. Organizations must understand the potential blast radius, particularly if exploited in multi-user environments. Given the CVSS score and the nature of this vulnerability, organizations should address it in priority 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 releases of Windows 10 (1607, 1809, 21H2, 22H2) and Windows 11 (23H2, 24H2, 25H2), along with multiple versions of Windows Server (2012, 2016, 2019, 2022 and 2025). Systems running these versions must be patched to prevent exploitation.
Mitigation & Remediation
Organizations should prioritize patching their systems to remediate this high-severity vulnerability. The latest patches for affected Microsoft products can be found in the Microsoft Security Update Guide. If a patch is not available, organizations should implement configuration hardening and network controls to mitigate risks. Continuous monitoring for vulnerabilities should be performed to ensure security.
Detection Guidance
Monitoring systems for behavioral anomalies and logging indicators related to unauthorized privilege escalation attempts is crucial. Additionally, organizations should focus on network signatures that could indicate exploitation attempts and track changes in system configurations.
AppSecure Threat Intelligence Insight
CVE-2026-21236 highlights the ongoing need for organizations to maintain vigilance over their systems. This vulnerability represents a broader trend of privilege escalation vulnerabilities that can be exploited locally. Security teams should assess their defenses and consider implementing a comprehensive vulnerability management program to identify and address such weaknesses. For more information on vulnerability management, check our guide on vulnerability management.
In addition, the importance of regularly conducting penetration testing cannot be overstated. For further insights on effective penetration testing strategies, refer to our penetration testing methodology.
Lastly, exploring how to improve your overall security posture through continuous security assessments is vital. Learn more about the benefits of continuous security testing.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
.webp)