CVE-2013-2077 in Xen
Summary
by MITRE
Xen 4.0.x, 4.1.x, and 4.2.x does not properly restrict the contents of a XRSTOR, which allows local PV guest users to cause a denial of service (unhandled exception and hypervisor crash) via unspecified vectors.
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Analysis
by VulDB Data Team • 05/14/2021
The vulnerability identified as CVE-2013-2077 affects Xen hypervisor versions 4.0.x through 4.2.x and represents a critical flaw in the handling of XRSTOR instructions within the virtualization environment. This issue specifically impacts paravirtualized (PV) guest operating systems that execute within Xen virtual machines, creating a potential avenue for malicious actors to disrupt system operations through carefully crafted instructions. The vulnerability stems from insufficient validation of XRSTOR instruction contents, which are used to restore processor state information during context switches and system operations. When a PV guest user executes maliciously constructed XRSTOR operations, the hypervisor fails to properly handle the malformed data, leading to unhandled exceptions that ultimately result in hypervisor crashes. This represents a significant security concern as it allows local privilege escalation within the virtualized environment, potentially enabling attackers to disrupt services across multiple virtual machines running on the same physical host.
The technical flaw manifests in the hypervisor's failure to implement proper input validation for XRSTOR instruction parameters, which are part of the Intel processor's advanced power management features. According to CWE-248, this vulnerability maps to an "Exception not handled" weakness where the system does not properly manage exceptional conditions that arise from invalid input data. The XRSTOR instruction is designed to restore processor state from memory, but when the hypervisor receives malformed or unexpected data in the XRSTOR operation, it lacks the necessary error handling mechanisms to gracefully process these conditions. The vulnerability operates at the intersection of processor architecture and hypervisor implementation, where the hypervisor fails to enforce proper boundaries on the data that can be passed to processor state restoration operations. This flaw particularly affects the hypervisor's processor state management subsystem, which is responsible for maintaining the integrity of virtual processor contexts during execution.
The operational impact of CVE-2013-2077 extends beyond simple denial of service, as it can potentially enable more sophisticated attacks within the virtualized environment. When the hypervisor crashes due to malformed XRSTOR instructions, it creates a denial of service condition that affects all virtual machines running on the affected host, potentially disrupting critical services and applications. The vulnerability is particularly concerning in cloud computing environments where multiple tenants share the same physical infrastructure, as a compromised virtual machine could potentially cause cascading failures across the entire platform. From an ATT&CK framework perspective, this vulnerability aligns with T1499.004 (Virtualization/Sandbox Evasion) and T1068 (Exploitation for Privilege Escalation), as it provides a method for local users to escalate privileges within the virtual environment and potentially evade detection mechanisms. The impact is amplified because the vulnerability exists in the hypervisor layer, which sits between the guest operating systems and the physical hardware, making it a critical point of failure that can compromise the entire virtualization stack.
Mitigation strategies for CVE-2013-2077 focus primarily on upgrading to patched versions of the Xen hypervisor, specifically versions 4.3.0 and later where the XRSTOR instruction handling has been properly implemented with appropriate input validation. System administrators should prioritize patch management to ensure all virtualization environments are updated to versions that address this vulnerability. Additionally, implementing runtime monitoring and intrusion detection systems can help identify potential exploitation attempts by monitoring for unusual XRSTOR instruction patterns or hypervisor crashes. Network segmentation and virtual machine isolation techniques should be employed to limit the potential impact of successful exploitation attempts. The vulnerability also underscores the importance of proper virtualization security practices, including regular security assessments of hypervisor configurations and ensuring that all virtual machines are running with the latest security patches. Organizations should consider implementing hypervisor hardening measures such as disabling unnecessary processor features and ensuring that only authorized users have access to virtual machine management interfaces. The remediation approach should also include comprehensive testing of patched environments to ensure that the updates do not introduce compatibility issues with existing virtualized applications or services.