CVE-2013-6938 in NetScaler SDX
Summary
by MITRE
Unspecified vulnerability in the Service VM in Citrix NetScaler SDX 9.3 before 9.3-64.4 and 10.0 before 10.0-77.5 and Application Delivery Controller (ADC) 9.3.x before 9.3-64.4, 10.0 before 10.0-77.5, and 10.1 before 10.1-118.7 allows attackers to cause a denial of service via unknown vectors, related to the "Virtual Machine Daemon."
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Analysis
by VulDB Data Team • 05/07/2026
The vulnerability identified as CVE-2013-6938 represents a critical security flaw within Citrix NetScaler SDX and ADC platforms that affects multiple version ranges including 9.3.x before 9.3-64.4, 10.0 before 10.0-77.5, and 10.1 before 10.1-118.7. This issue resides within the Service VM component specifically affecting the Virtual Machine Daemon which serves as a foundational element for virtualized service delivery within the Citrix infrastructure. The unspecified nature of the vulnerability vectors suggests that attackers can exploit various attack surfaces within this daemon component to disrupt service availability, making the flaw particularly concerning for enterprise environments that rely heavily on Citrix's application delivery and networking solutions.
The technical implementation of this vulnerability stems from weaknesses within the Virtual Machine Daemon functionality that governs how service virtual machines operate within the Citrix NetScaler environment. This daemon component is responsible for managing virtual machine lifecycle operations, resource allocation, and service orchestration within the SDX platform. When compromised, the daemon can become unstable or crash, leading to complete service disruption for applications and services that depend on the affected Citrix appliances. The vulnerability's classification as a denial of service issue indicates that attackers can leverage the flaw to force the daemon to terminate unexpectedly or consume excessive system resources, thereby rendering the network services unavailable to legitimate users. This type of vulnerability aligns with CWE-119 which addresses weaknesses in memory management and resource handling, particularly in daemon processes that must maintain stability under various operational conditions.
The operational impact of CVE-2013-6938 extends beyond simple service interruption to potentially compromise the entire network infrastructure that relies on Citrix NetScaler appliances for application delivery and load balancing. Organizations utilizing affected versions may experience significant downtime as the Virtual Machine Daemon becomes unstable, causing cascading failures across dependent services. Network administrators face the challenge of identifying vulnerable systems within their infrastructure since the unspecified attack vectors make it difficult to predict exactly how an attacker might exploit the weakness. The vulnerability particularly affects enterprise environments where Citrix appliances serve as critical components for delivering web applications, managing traffic loads, and ensuring service availability. Attackers could potentially leverage this vulnerability to conduct sustained denial of service attacks against critical business applications, leading to financial losses and reputation damage. The impact is exacerbated by the fact that many organizations may not immediately detect the vulnerability due to the lack of specific attack patterns and the complex nature of the underlying daemon operations.
Mitigation strategies for CVE-2013-6938 primarily focus on applying the vendor-provided patches and updates that address the specific Virtual Machine Daemon instability issues. Organizations should prioritize immediate deployment of Citrix security patches for versions 9.3-64.4, 10.0-77.5, and 10.1-118.7 to resolve the vulnerability. System administrators should conduct comprehensive vulnerability assessments to identify all affected Citrix appliances within their network infrastructure, particularly focusing on SDX platforms and ADC deployments. Network monitoring should be enhanced to detect unusual daemon behavior or resource consumption patterns that might indicate exploitation attempts. The implementation of network segmentation and access controls can help limit the potential attack surface for this vulnerability. Additionally, organizations should consider implementing intrusion detection systems that can monitor for anomalous daemon behavior and establish incident response procedures specifically tailored to address service daemon failures. From an ATT&CK framework perspective, this vulnerability maps to T1499 which covers network disruption techniques, and T1070 which addresses indicator removal and system manipulation. Organizations should also implement proper change management procedures to ensure that all security updates are applied consistently across their Citrix infrastructure while maintaining detailed logs of system modifications for audit and forensic purposes.