CVE-2014-1642 in Xen
Summary
by MITRE
The IRQ setup in Xen 4.2.x and 4.3.x, when using device passthrough and configured to support a large number of CPUs, frees certain memory that may still be intended for use, which allows local guest administrators to cause a denial of service (memory corruption and hypervisor crash) and possibly execute arbitrary code via vectors related to an out-of-memory error that triggers a (1) use-after-free or (2) double free.
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Analysis
by VulDB Data Team • 06/08/2021
The vulnerability identified as CVE-2014-1642 represents a critical memory management flaw within the Xen hypervisor version 4.2.x and 4.3.x, specifically affecting systems utilizing device passthrough configurations with extensive CPU support. This issue stems from improper memory deallocation during interrupt request setup processes, creating a dangerous condition where memory regions intended for active use are prematurely freed. The flaw manifests when hypervisors configure interrupt handling for devices passed through to guest operating systems, particularly in environments supporting numerous CPU cores. The vulnerability impacts systems where guest administrators can influence the hypervisor's memory allocation patterns through device passthrough mechanisms, making it particularly concerning for multi-tenant cloud environments and virtualized infrastructure where guest users might have administrative privileges.
The technical root cause of this vulnerability lies in the hypervisor's failure to properly track memory references during interrupt handling setup operations, resulting in either use-after-free or double free conditions. When the system encounters memory exhaustion scenarios during device passthrough operations, the IRQ setup code attempts to free memory blocks that remain referenced by active processes or data structures. This improper memory management creates opportunities for attackers to manipulate the hypervisor's memory state through carefully crafted device configuration changes or resource allocation patterns. The vulnerability operates under the Common Weakness Enumeration framework as CWE-415, specifically addressing improper free conditions and memory management errors that can lead to arbitrary code execution or system crashes. The flaw demonstrates characteristics of both use-after-free vulnerabilities and double free conditions, where memory is freed twice or accessed after being freed, potentially allowing attackers to corrupt memory structures and gain elevated privileges.
The operational impact of CVE-2014-1642 extends beyond simple denial of service to encompass potential privilege escalation and system compromise within virtualized environments. Local guest administrators can exploit this vulnerability to cause hypervisor crashes, leading to service disruption across all virtual machines hosted on the affected system, while simultaneously creating opportunities for memory corruption that could enable arbitrary code execution. This vulnerability particularly affects cloud computing environments and data centers where multiple tenants share the same hypervisor infrastructure, as guest administrators might leverage this flaw to compromise the integrity of the host system and potentially access other virtual machines. The attack vector requires the attacker to have administrative access within a guest operating system and the ability to configure device passthrough, which is common in virtualized environments where users require direct hardware access for performance optimization or specialized applications. The vulnerability's severity is amplified by the fact that it can be exploited without requiring special privileges beyond those normally available to guest administrators, making it particularly dangerous in multi-tenant deployments.
Mitigation strategies for CVE-2014-1642 focus primarily on updating to patched versions of Xen hypervisor, specifically versions 4.4.0 and later, which contain proper memory management fixes for the IRQ setup process. Organizations should implement immediate patch management procedures to upgrade all affected hypervisor installations, particularly in production environments where guest administrators have elevated privileges. Additional protective measures include restricting device passthrough capabilities for guest operating systems, implementing strict access controls for virtual machine configuration, and monitoring memory allocation patterns for suspicious activity. Network segmentation and isolation of virtualized environments can help limit the potential impact if exploitation occurs. The vulnerability highlights the importance of proper memory management in hypervisor code and demonstrates why security patches for virtualization platforms must be prioritized. Organizations should also consider implementing runtime monitoring solutions that can detect anomalous memory behavior patterns indicative of use-after-free conditions, as these systems can provide early warning of potential exploitation attempts. The remediation process should include thorough testing of patched hypervisor versions to ensure compatibility with existing virtual machine configurations and applications running in the virtualized environment.