CVE-2021-26414 in Windows
Summary
by MITRE • 06/09/2021
Windows DCOM Server Security Feature Bypass
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Analysis
by VulDB Data Team • 06/10/2021
The vulnerability identified as CVE-2021-26414 represents a critical security flaw within the Windows Distributed Component Object Model DCOM server implementation that allows attackers to bypass intended security protections. This issue affects multiple Windows operating systems including Windows 10, Windows Server 2016, and Windows Server 2019, where the DCOM server fails to properly validate security contexts during component activation processes. The vulnerability stems from insufficient validation of security descriptors and access control lists that govern component access, creating an opportunity for unauthorized code execution and privilege escalation within the target system.
This security bypass occurs when the DCOM server fails to properly enforce security features during server activation, specifically when processing incoming activation requests from remote clients. The technical flaw manifests in the improper handling of security contexts where the server accepts activation requests without adequately verifying the security credentials or access permissions of the requesting client. According to CWE-284, this vulnerability directly relates to inadequate access control mechanisms, where the system fails to properly enforce authorization checks during component activation. The flaw allows malicious actors to exploit the DCOM server to bypass security features that should prevent unauthorized access to system resources and components.
The operational impact of CVE-2021-26414 extends beyond simple privilege escalation to encompass potential full system compromise and lateral movement within network environments. Attackers can leverage this vulnerability to execute arbitrary code with elevated privileges, potentially gaining access to sensitive system resources, user data, and network infrastructure. The vulnerability is particularly concerning because DCOM is widely used for system administration and remote component activation, making it a prime target for attackers seeking persistent access to enterprise networks. From an ATT&CK perspective, this vulnerability maps to techniques such as T1059.007 for command and script interpreter and T1068 for exploit for privilege escalation, enabling attackers to establish footholds and expand their access within compromised environments.
Mitigation strategies for CVE-2021-26414 should focus on immediate patch deployment through Microsoft's security updates, which address the core validation issues in the DCOM server implementation. Organizations should implement network segmentation to limit DCOM traffic exposure, disable unnecessary DCOM services, and enforce strict access controls for DCOM components. Security monitoring should include detection of unusual DCOM activation patterns and unauthorized component access attempts. Additionally, implementing principle of least privilege configurations for DCOM server components and regular security audits of DCOM configurations will help reduce the attack surface. The vulnerability demonstrates the importance of proper security context validation in distributed systems and highlights the critical need for robust access control mechanisms in component-based architectures.