A significant security vulnerability, identified as CVE-2025-6759, has been discovered in Citrix’s Windows Virtual Delivery Agent (VDA), a core component of Citrix Virtual Apps and Desktops and Citrix DaaS. This flaw enables local users with limited privileges to escalate their access rights to SYSTEM level, posing a substantial risk to affected systems.
Understanding CVE-2025-6759
CVE-2025-6759 is classified under CWE-269 (Improper Privilege Management) and has been assigned a CVSS v4.0 Base Score of 7.3, indicating high severity. The vulnerability allows a low-privileged user to gain SYSTEM privileges, the highest level of access in Windows environments. Exploitation requires local access to the target system, meaning the attacker must already have some form of access to the machine. Once exploited, the attacker can perform actions such as installing software, accessing sensitive data, creating new accounts with full user rights, and potentially moving laterally within the network.
Affected Versions
The vulnerability specifically impacts the Windows Virtual Delivery Agent for single-session operating systems used by Citrix Virtual Apps and Desktops and Citrix DaaS. The affected versions include:
– Current Release (CR): Citrix Virtual Apps and Desktops versions before 2503.
– Long Term Service Release (LTSR): Citrix Virtual Apps and Desktops 2402 LTSR CU2 and earlier versions.
Notably, Citrix Virtual Apps and Desktops 2203 LTSR is not affected by this vulnerability, providing some relief for organizations using this specific version.
Mitigation Strategies
Citrix strongly recommends that customers upgrade their Windows Virtual Delivery Agent for single-session OS to versions that contain the fixes as soon as possible. The versions that contain the fixes are:
– Current Release (CR): Citrix Virtual Apps and Desktops 2503 and later versions.
– Long Term Service Release (LTSR): Citrix Virtual Apps and Desktops 2402 LTSR CU1 Update 1 and Citrix Virtual Apps and Desktops 2402 LTSR CU2 Update 1.
For organizations unable to apply patches immediately, Citrix has provided a registry-level workaround. This involves setting the registry key `HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\CtxExceptionHandler` with the value `Enabled=dword:00000000`. While this is a temporary measure, it is not a substitute for applying the recommended updates.
Implications for Enterprise Environments
The discovery of CVE-2025-6759 underscores the critical importance of maintaining up-to-date systems and promptly applying security patches. In enterprise environments where Citrix Virtual Apps and Desktops are widely deployed, the potential for privilege escalation to SYSTEM level can have severe consequences, including unauthorized access to sensitive data, disruption of services, and the potential for further exploitation within the network.
Organizations should assess their current deployments, identify affected systems, and prioritize the application of the recommended updates. Additionally, implementing the temporary registry workaround can provide interim protection until the patches can be applied.
Conclusion
CVE-2025-6759 represents a significant security risk for organizations utilizing Citrix’s Windows Virtual Delivery Agent. Prompt action is essential to mitigate this vulnerability. By upgrading to the patched versions or applying the temporary workaround, organizations can protect their systems from potential exploitation and maintain the integrity and security of their virtual desktop infrastructure.
