CVE-2015-2045 in Xen
Summary
by MITRE
The HYPERVISOR_xen_version hypercall in Xen 3.2.x through 4.5.x does not properly initialize data structures, which allows local guest users to obtain sensitive information via unspecified vectors.
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Analysis
by VulDB Data Team • 03/11/2022
The HYPERVISOR_xen_version hypercall vulnerability in Xen hypervisor versions 3.2.x through 4.5.x represents a critical information disclosure flaw that stems from improper data structure initialization within the hypervisor's hypercall interface. This vulnerability specifically affects the xen_version hypercall which is designed to provide version information about the Xen hypervisor to guest operating systems. The flaw occurs when the hypercall fails to properly initialize memory structures before populating them with version data, creating a scenario where sensitive information from the hypervisor's memory space may be inadvertently exposed to unprivileged guest users.
The technical implementation of this vulnerability involves the hypercall mechanism that allows guest operating systems to communicate with the hypervisor kernel through a well-defined interface. When guest users invoke the HYPERVISOR_xen_version hypercall, the hypervisor should properly initialize the data structures that will contain the version information before writing the actual version data into these structures. However, due to insufficient initialization, memory regions that should remain pristine may contain residual data from previous operations or internal hypervisor state, which gets exposed to the guest user space through the hypercall response.
This vulnerability falls under the CWE-125 Out-of-bounds Read category, as it involves reading memory locations that have not been properly initialized, potentially exposing data that should remain confidential. The operational impact of this vulnerability is significant because local guest users can exploit this flaw to gain access to sensitive information that may include internal hypervisor memory layouts, kernel addresses, or other confidential data structures. The exposure of such information could potentially aid attackers in developing more sophisticated attacks against the hypervisor or the guest operating systems running on top of it.
The attack vector for this vulnerability is particularly concerning as it requires only local access within a guest operating system, making it accessible to any user with access to the guest environment. This means that an attacker who has compromised a guest VM could potentially use this vulnerability to escalate their privileges or gather intelligence about the underlying hypervisor infrastructure. The vulnerability is classified under the MITRE ATT&CK technique T1059.001 Command and Scripting Interpreter and T1068 Exploitation for Privilege Escalation, as it provides a pathway for privilege escalation through information gathering and potential exploitation of the hypervisor's memory layout.
Mitigation strategies for this vulnerability include updating to Xen hypervisor versions 4.6.x or later where the hypercall implementation has been corrected to properly initialize data structures before populating them with version information. System administrators should also implement proper access controls and monitoring to detect potential exploitation attempts. The vulnerability demonstrates the importance of proper memory initialization in hypervisor interfaces and highlights the need for comprehensive testing of hypercall implementations to prevent information disclosure vulnerabilities that could compromise the security of the entire virtualization infrastructure.