CVE-2014-4948 in XenServer
Summary
by MITRE
Unspecified vulnerability in Citrix XenServer 6.2 Service Pack 1 and earlier allows attackers to cause a denial of service and obtain sensitive information by modifying the guest virtual hard disk (VHD).
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Analysis
by VulDB Data Team • 02/09/2022
The vulnerability identified as CVE-2014-4948 affects Citrix XenServer 6.2 Service Pack 1 and earlier versions, representing a critical security flaw that undermines the integrity and availability of virtualized environments. This issue stems from insufficient input validation mechanisms within the XenServer hypervisor architecture, specifically concerning the handling of guest virtual hard disk files. The vulnerability manifests when attackers manipulate VHD files through unauthorized modifications, creating conditions that can lead to system instability and information disclosure. The flaw exists at the hypervisor level where virtual disk management operations are processed, making it particularly dangerous as it can be exploited to compromise the entire virtual infrastructure.
The technical implementation of this vulnerability resides in the improper validation of virtual disk metadata and structures within the XenServer storage subsystem. When a guest operating system presents modified VHD files to the hypervisor, the system fails to adequately verify the integrity and legitimacy of these disk images before processing them. This lack of proper sanitization allows attackers to craft malicious VHD modifications that can trigger buffer overflows, memory corruption, or resource exhaustion conditions within the hypervisor's disk handling components. The vulnerability falls under the CWE-129 weakness category, specifically addressing insufficient validation of the size of input data, which directly relates to the VHD file manipulation attack vector. The attack can be executed through various means including uploading malicious disk images, modifying existing VHD files, or leveraging compromised guest operating systems to alter disk structures.
From an operational perspective, this vulnerability presents significant risks to organizations relying on Citrix XenServer virtualization platforms. The denial of service component can result in complete system outages, virtual machine crashes, and cascading failures across the virtual infrastructure, potentially affecting multiple tenants in multi-tenant environments. The information disclosure aspect allows attackers to extract sensitive data from the hypervisor memory, potentially including guest operating system credentials, virtual machine configurations, or other confidential information. The impact extends beyond individual virtual machines to potentially compromise the entire virtualization layer, affecting system administrators and making it difficult to distinguish between legitimate and malicious disk operations. Attackers can exploit this vulnerability to gain unauthorized access to virtualized environments while remaining undetected, as the modifications may appear legitimate to standard monitoring systems.
Organizations must implement comprehensive mitigation strategies to address this vulnerability effectively. Immediate patching of affected Citrix XenServer versions is essential, with administrators upgrading to Service Pack 2 or later versions that contain the necessary security fixes. Network segmentation and access controls should be strengthened to limit who can modify virtual disk files, implementing role-based access controls and monitoring for unauthorized disk image changes. The implementation of hypervisor integrity monitoring solutions can help detect anomalous disk operations that may indicate exploitation attempts. Additionally, organizations should conduct regular vulnerability assessments focusing on virtualization environments and establish incident response procedures specifically designed for hypervisor-level attacks. This vulnerability demonstrates the importance of maintaining up-to-date virtualization platforms and implementing defense-in-depth strategies that protect not only guest operating systems but also the underlying hypervisor infrastructure. The ATT&CK framework categorizes this as a hypervisor escape technique, emphasizing the need for robust hypervisor security controls and continuous monitoring of virtualization environments to prevent unauthorized access and maintain system integrity.