CVE-2013-2072 in Xen
Summary
by MITRE
Buffer overflow in the Python bindings for the xc_vcpu_setaffinity call in Xen 4.0.x, 4.1.x, and 4.2.x allows local administrators with permissions to configure VCPU affinity to cause a denial of service (memory corruption and xend toolstack crash) and possibly gain privileges via a crafted cpumap.
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Analysis
by VulDB Data Team • 05/11/2021
The vulnerability identified as CVE-2013-2072 represents a critical buffer overflow flaw within the Python bindings of the Xen hypervisor's xc_vcpu_setaffinity API call. This issue affects Xen versions 4.0.x through 4.2.x and specifically targets the virtual CPU affinity configuration functionality that allows administrators to assign virtual CPUs to specific physical CPU cores. The flaw exists in the Python interface layer that communicates with the underlying hypervisor, creating a potential attack vector for local administrators who possess the necessary permissions to configure VCPU affinity settings. The vulnerability manifests when the cpumap parameter is processed without adequate bounds checking, leading to memory corruption that can result in system instability and complete toolstack crashes.
The technical implementation of this vulnerability stems from improper input validation within the Python bindings that handle the xc_vcpu_setaffinity call. When a crafted cpumap value is provided, the buffer allocated for processing this parameter exceeds its intended capacity, causing adjacent memory locations to be overwritten. This memory corruption directly impacts the xend toolstack which manages Xen virtual machines, leading to unpredictable behavior including segmentation faults and system crashes. The vulnerability is particularly concerning because it requires only local administrative privileges to exploit, making it accessible to users with VCPU affinity configuration permissions rather than requiring more elevated privileges.
The operational impact of CVE-2013-2072 extends beyond simple denial of service to potentially enable privilege escalation attacks. While the primary effect is memory corruption and xend toolstack crashes, the underlying buffer overflow condition creates opportunities for attackers to manipulate memory contents in ways that could allow for code execution or privilege elevation. The vulnerability affects the core hypervisor functionality that manages CPU scheduling and resource allocation for virtual machines, potentially compromising the integrity of the entire virtualization environment. Systems running affected Xen versions are particularly vulnerable in environments where local administrators have access to VCPU affinity configuration capabilities, creating a significant risk for cloud computing platforms and virtualized infrastructure deployments.
Security mitigations for this vulnerability should focus on immediate patching of affected Xen versions to address the buffer overflow in the Python bindings. Organizations should implement strict access controls to limit VCPU affinity configuration permissions to only essential administrative users. The fix typically involves implementing proper bounds checking and input validation within the Python interface layer before processing cpumap parameters. Additionally, monitoring systems should be enhanced to detect unusual patterns in VCPU affinity configuration changes that could indicate exploitation attempts. This vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and maps to ATT&CK technique T1068, involving exploitation of remote services, though in this case the attack vector is local rather than remote. Organizations should also consider implementing intrusion detection systems that can identify abnormal memory access patterns consistent with buffer overflow exploitation attempts.