CVE-2021-22928 in Virtual Apps
Summary
by MITRE • 08/06/2021
A vulnerability has been identified in Citrix Virtual Apps and Desktops that could, if exploited, allow a user of a Windows VDA that has either Citrix Profile Management or Citrix Profile Management WMI Plugin installed to escalate their privilege level on that Windows VDA to SYSTEM.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 08/10/2021
This vulnerability resides within Citrix Virtual Apps and Desktops software ecosystem, specifically targeting the Windows Virtual Desktop Agent (VDA) components. The flaw manifests when Citrix Profile Management or the Citrix Profile Management WMI Plugin is installed on a Windows VDA system, creating a privilege escalation vector that could be exploited by malicious actors. The vulnerability represents a critical security gap that allows local users to elevate their privileges from standard user level to SYSTEM level access, effectively granting them complete control over the affected Windows VDA instance.
The technical implementation of this vulnerability stems from improper privilege handling within the Citrix Profile Management components. When these components execute certain operations, they fail to properly validate or restrict user permissions, creating an opportunity for privilege escalation. The flaw specifically affects systems where the WMI plugin is installed, as the underlying Windows Management Instrumentation framework provides mechanisms that can be manipulated to gain elevated privileges. This issue aligns with CWE-276, which describes improper privilege management, and represents a classic local privilege escalation vulnerability that operates within the Windows security model. The vulnerability exploits the trust relationships between system components and user contexts, allowing malicious code execution with elevated privileges.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally compromises the security posture of any Citrix VDA environment where the affected components are deployed. Once an attacker achieves SYSTEM-level access, they can manipulate system files, install malicious software, access all user data, and potentially use the compromised VDA as a pivot point to attack other systems within the network infrastructure. The vulnerability affects organizations that rely on Citrix Profile Management for user profile handling, which is common in enterprise environments where user experience and profile persistence are critical requirements. This creates a significant risk for organizations with large Citrix deployments, as the compromise of a single VDA could provide attackers with a foothold to escalate their access across multiple systems.
Mitigation strategies for this vulnerability should include immediate patch application from Citrix, which addresses the privilege escalation flaw through proper access control implementation. Organizations should also implement network segmentation to limit lateral movement opportunities and monitor for suspicious privilege escalation activities using security information and event management tools. The principle of least privilege should be enforced by limiting the installation of unnecessary Citrix Profile Management components and ensuring that only authorized users have access to systems with these plugins installed. Additionally, regular security assessments should be conducted to identify and remediate similar privilege management issues within the broader Citrix environment and associated systems. Organizations should also consider implementing endpoint detection and response solutions to identify anomalous behavior patterns that may indicate exploitation attempts. The vulnerability demonstrates the importance of proper privilege management in enterprise environments and highlights the need for continuous security monitoring and rapid patch deployment processes.