CVE-2012-5525 in Xen
Summary
by MITRE
The get_page_from_gfn hypercall function in Xen 4.2 allows local PV guest OS administrators to cause a denial of service (crash) via a crafted GFN that triggers a buffer over-read.
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Analysis
by VulDB Data Team • 04/20/2021
The vulnerability identified as CVE-2012-5525 represents a critical buffer over-read flaw within the Xen hypervisor's get_page_from_gfn hypercall function. This issue affects Xen version 4.2 and specifically targets the interaction between the hypervisor and paravirtualized guest operating systems. The vulnerability stems from insufficient validation of guest-provided GFN (Guest Frame Number) values during hypercall processing, creating a scenario where maliciously crafted input can trigger memory corruption within the hypervisor's execution context. The flaw exists in the hypervisor's memory management subsystem where it processes memory requests from guest VMs without proper bounds checking on the frame number parameters.
The technical implementation of this vulnerability exploits the fundamental architecture of Xen's memory management system where guest VMs communicate with the hypervisor through hypercalls to access physical memory pages. When a paravirtualized guest administrator invokes the get_page_from_gfn hypercall with a malformed GFN value, the hypervisor's kernel code fails to validate the input boundaries before attempting to access memory locations. This results in a buffer over-read condition where the hypervisor attempts to read beyond allocated memory boundaries, potentially accessing invalid memory regions or triggering memory corruption that leads to system instability. The flaw is particularly dangerous because it can be exploited by local administrators within a guest VM, bypassing traditional network-based attack vectors.
From an operational perspective, this vulnerability presents a significant threat to virtualized environments where multiple tenants share the same hypervisor infrastructure. The ability to cause a denial of service through a local guest administrator means that a compromised or malicious guest VM can potentially crash the entire host system, affecting all other VMs running on the same physical hardware. This represents a direct violation of the isolation principles that virtualization platforms are designed to maintain. The impact extends beyond simple service disruption as hypervisor crashes can lead to data loss, service interruptions, and potential compromise of the entire virtualized infrastructure. The vulnerability also enables potential privilege escalation scenarios where attackers might leverage the hypervisor instability to gain deeper access to the underlying system resources.
The mitigation strategies for CVE-2012-5525 primarily involve immediate patching of the Xen hypervisor to version 4.2.1 or later, which includes proper input validation and bounds checking for the get_page_from_gfn hypercall. Organizations should implement comprehensive monitoring of hypervisor logs for unusual hypercall patterns and memory access anomalies that might indicate exploitation attempts. Additionally, network segmentation and access controls should be strengthened to limit the potential impact of compromised guest VMs. The vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and relates to ATT&CK technique T1059.001 for command and scripting interpreter execution. Security teams should also consider implementing hypervisor-level memory protection mechanisms and regular security assessments of virtualized environments to detect similar vulnerabilities in the hypervisor's memory management subsystem. Organizations must ensure that all virtualization platforms are kept up-to-date with the latest security patches and that proper isolation measures are maintained between guest VMs to prevent lateral movement and escalation attacks.