CVE-2012-5510 in Xen
Summary
by MITRE
Xen 4.x, when downgrading the grant table version, does not properly remove the status page from the tracking list when freeing the page, which allows local guest OS administrators to cause a denial of service (hypervisor crash) via unspecified vectors.
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Analysis
by VulDB Data Team • 12/20/2021
The vulnerability identified as CVE-2012-5510 affects the Xen hypervisor version 4.x family and represents a critical flaw in the grant table management system that can lead to hypervisor instability. This issue specifically manifests during the process of downgrading grant table versions, where the hypervisor fails to properly handle the removal of status pages from its tracking mechanisms when freeing memory pages. The flaw exists in the hypervisor's memory management subsystem and particularly impacts how it tracks and manages grant table pages that are being deallocated during version transitions.
The technical implementation of this vulnerability stems from inadequate cleanup procedures within the grant table handling code. When a guest operating system attempts to downgrade the grant table version, the hypervisor must properly manage the lifecycle of status pages that are associated with grant table entries. However, the flaw occurs during the deallocation phase where the hypervisor neglects to remove the status page from its internal tracking list before freeing the memory. This creates a scenario where the hypervisor maintains references to freed memory locations, leading to potential memory corruption or invalid memory access patterns that can ultimately result in hypervisor crashes.
The operational impact of this vulnerability is significant as it allows local guest OS administrators to execute a denial of service attack against the hypervisor without requiring elevated privileges. This means that any user with administrative access within a guest operating system can potentially trigger a hypervisor crash, effectively compromising the stability of the entire virtualization environment. The attack vector is particularly concerning because it operates at the hypervisor level, affecting all virtual machines running on the same host system, potentially causing widespread service disruption across multiple guest environments.
This vulnerability aligns with CWE-459, which describes improper cleanup of resources, and specifically relates to improper handling of grant table version transitions in virtualization environments. The flaw can be mapped to ATT&CK technique T1499.001, which covers network denial of service attacks, and T1068, which covers exploit for privilege escalation, as the local administrator can leverage this to cause hypervisor instability. The security implications extend beyond simple denial of service as the memory corruption patterns could potentially be exploited to achieve more sophisticated attacks if combined with other vulnerabilities.
Mitigation strategies for this vulnerability should focus on implementing proper memory management procedures within the hypervisor's grant table handling code. System administrators should immediately apply the vendor-provided patches that address the grant table version downgrade logic and ensure that all hypervisor components are updated to versions that contain the necessary fixes. Additionally, monitoring systems should be enhanced to detect unusual patterns in grant table operations and memory management activities that could indicate exploitation attempts. Regular security assessments of virtualization environments should include checks for proper resource cleanup procedures and memory management integrity. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of such vulnerabilities, while maintaining strict update policies for virtualization infrastructure components to prevent similar issues from arising in the future.