CVE-2013-0215 in Xen
Summary
by MITRE
oxenstored in Xen 4.1.x, Xen 4.2.x, and xen-unstable does not properly consider the state of the Xenstore ring during read operations, which allows guest OS users to cause a denial of service (daemon crash and host-control outage, or memory consumption) or obtain sensitive control-plane data by leveraging guest administrative access.
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Analysis
by VulDB Data Team • 05/04/2021
The vulnerability identified as CVE-2013-0215 represents a critical flaw in the Xen hypervisor's implementation of the xenstore daemon, specifically affecting versions 4.1.x, 4.2.x, and xen-unstable branches. This issue resides within the core virtualization infrastructure that manages communication between guest operating systems and the hypervisor's control plane. The xenstore daemon serves as a crucial component for maintaining state information and configuration data across the virtualized environment, making it a prime target for exploitation by malicious actors who have gained administrative access within guest VMs. The vulnerability stems from improper handling of the xenstore ring buffer state during read operations, creating a fundamental security gap that can be leveraged for both denial of service and information disclosure attacks.
The technical flaw manifests when guest operating systems with administrative privileges attempt to interact with the xenstore daemon through read operations on the ring buffer. The vulnerability occurs because the daemon fails to properly validate or account for the current state of the ring buffer before processing read requests. This improper state consideration allows attackers to craft specific sequences of xenstore operations that can either cause the daemon to crash, leading to complete host-control outages, or manipulate memory consumption patterns to exhaust system resources. The ring buffer mechanism in xenstore is designed to facilitate efficient communication between hypervisor and guest components, but the flawed implementation means that malicious read operations can disrupt normal operation flow and potentially expose sensitive control-plane data.
The operational impact of this vulnerability extends beyond simple service disruption to encompass potential data compromise and system instability. When exploited successfully, attackers with guest administrative access can trigger daemon crashes that result in complete host-control outages, effectively rendering the hypervisor unresponsive and potentially causing all virtual machines running on that host to become inaccessible. Additionally, the vulnerability enables memory consumption attacks where malicious actors can force the xenstore daemon to consume excessive memory resources, leading to system resource exhaustion and further denial of service conditions. The ability to obtain sensitive control-plane data represents a particularly concerning aspect, as this information could include configuration details, security parameters, or other privileged information that could be used to escalate attacks or compromise the integrity of the entire virtualization environment.
Mitigation strategies for CVE-2013-0215 should prioritize immediate patching of affected Xen hypervisor versions to the latest stable releases that contain the necessary fixes for the xenstore ring buffer state handling. Organizations should implement comprehensive monitoring of xenstore daemon behavior and memory usage patterns to detect potential exploitation attempts. The vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and relates to ATT&CK technique T1059 for execution through hypervisor manipulation. Security teams should also consider implementing network segmentation and access controls to limit guest administrative privileges, reducing the attack surface available to potential exploiters. Regular security assessments of virtualization environments and mandatory patch management procedures are essential for preventing exploitation of this and similar hypervisor-level vulnerabilities. The remediation process should include thorough testing of patched systems to ensure that the fix does not introduce compatibility issues with existing virtual machine configurations while maintaining the integrity of the xenstore communication mechanism.