CVE-2022-42334 in Xen
Summary
by MITRE • 03/21/2023
x86/HVM pinned cache attributes mis-handling T[his CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] To allow cachability control for HVM guests with passed through devices, an interface exists to explicitly override defaults which would otherwise be put in place. While not exposed to the affected guests themselves, the interface specifically exists for domains controlling such guests. This interface may therefore be used by not fully privileged entities, e.g. qemu running deprivileged in Dom0 or qemu running in a so called stub-domain. With this exposure it is an issue that - the number of the such controlled regions was unbounded (CVE-2022-42333), - installation and removal of such regions was not properly serialized (CVE-2022-42334).
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Analysis
by VulDB Data Team • 04/12/2023
The vulnerability described in CVE-2022-42334 represents a critical flaw in the handling of memory cache attributes within Intel x86 Hypervisor Virtual Machine (HVM) environments. This issue specifically affects the management of pinned cache attributes for virtual machines that utilize passthrough devices, creating a potential attack surface that could be exploited by malicious actors with access to hypervisor management interfaces. The vulnerability resides in the Xen hypervisor implementation where cacheability control mechanisms are improperly managed during memory region allocation and deallocation processes. The affected system operates under the assumption that cache attributes for hardware virtual machines can be explicitly overridden through dedicated interfaces, which are designed for domain-level management rather than guest-level access, yet these interfaces contain critical implementation flaws that allow for resource exhaustion and potential privilege escalation.
The technical flaw manifests in the improper serialization of cache region installation and removal operations within the hypervisor's memory management subsystem. When virtual machines utilize passthrough devices, the hypervisor must maintain explicit cache attribute controls for memory regions associated with these devices to ensure proper hardware behavior and performance characteristics. The vulnerability stems from the lack of proper synchronization mechanisms during the dynamic allocation and deallocation of these cache regions, which creates opportunities for race conditions and resource management errors. This mis-handling directly violates the fundamental security principles of resource management in virtualized environments, as it allows for potential memory corruption and system instability through improper cache attribute handling. The issue is particularly concerning because it affects the core memory management operations that underpin virtual machine isolation and security boundaries, potentially enabling attackers to manipulate memory cache behavior in ways that could compromise system integrity.
The operational impact of CVE-2022-42334 extends beyond simple denial-of-service conditions to potentially enable more sophisticated attacks within virtualized environments. The unbounded nature of controlled memory regions combined with improper serialization creates opportunities for attackers to exhaust system resources through repeated allocation operations, leading to system instability and potential denial-of-service scenarios. This vulnerability is particularly dangerous in environments where hypervisor management interfaces are accessible to partially privileged entities such as qemu processes running in Dom0 or stub domains, as these entities may not have full administrative privileges but still possess the ability to manipulate memory cache attributes. The attack surface is further expanded by the fact that this vulnerability can be leveraged to compromise the integrity of memory management operations, potentially allowing for privilege escalation or information disclosure through cache-based side-channel attacks. The impact is measured in terms of system availability, data integrity, and the potential for lateral movement within virtualized infrastructures.
Mitigation strategies for CVE-2022-42334 require immediate attention through patching of affected Xen hypervisor versions and implementation of proper access controls for cache attribute management interfaces. Organizations should implement strict privilege controls to limit which entities can manipulate memory cache attributes, particularly ensuring that qemu processes running in Dom0 or stub domains have appropriate security boundaries. The recommended approach includes applying the latest security patches from Xen Project that address the serialization issues in cache region management and implementing monitoring solutions to detect anomalous cache attribute manipulation patterns. Additionally, system administrators should consider implementing memory resource limits and quotas for cache region allocation to prevent resource exhaustion attacks. The vulnerability aligns with CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization) and represents a significant concern under ATT&CK framework category T1059 (Command and Scripting Interpreter) through potential privilege escalation vectors. Proper configuration management and regular security assessments of hypervisor interfaces are essential to prevent exploitation of this vulnerability, particularly in cloud computing and virtualized environments where multiple tenants may share the same physical infrastructure.