CVE-2019-17351 in Xen
Summary
by MITRE
An issue was discovered in drivers/xen/balloon.c in the Linux kernel before 5.2.3, as used in Xen through 4.12.x, allowing guest OS users to cause a denial of service because of unrestricted resource consumption during the mapping of guest memory, aka CID-6ef36ab967c7.
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Analysis
by VulDB Data Team • 01/05/2024
The vulnerability identified as CVE-2019-17351 represents a critical denial of service weakness within the Linux kernel's Xen hypervisor balloon driver implementation. This flaw exists in the drivers/xen/balloon.c file and affects Linux kernel versions prior to 5.2.3, specifically impacting Xen hypervisor versions through 4.12.x. The issue stems from inadequate resource management during the memory mapping process, creating a scenario where malicious guest operating systems can exploit the system's memory allocation mechanisms to consume excessive resources. The vulnerability is particularly concerning because it operates at the hypervisor level, allowing guest users to directly influence host system resources and potentially compromise the stability of the entire virtualization environment.
The technical root cause of this vulnerability lies in the unrestricted memory mapping behavior within the balloon driver's implementation. When guest operating systems attempt to map memory regions, the driver fails to properly enforce resource limits or validate the magnitude of memory requests. This lack of proper resource boundary checking enables attackers to submit memory mapping requests that consume disproportionate amounts of host system resources, ultimately leading to resource exhaustion and system instability. The vulnerability operates under the Common Weakness Enumeration category of insufficient resource management, specifically falling under CWE-775 which addresses missing release of resource on exceptional path. The balloon driver's memory management logic does not adequately account for the potential for malicious or malformed memory mapping requests from guest systems, creating a pathway for resource starvation attacks.
From an operational impact perspective, this vulnerability enables guest users to perform denial of service attacks against the host system and potentially other guest instances within the same hypervisor environment. The unrestricted resource consumption can lead to complete system paralysis, where legitimate processes cannot allocate necessary memory resources, resulting in system crashes or unresponsiveness. In virtualized environments where multiple tenants share the same physical hardware, this vulnerability can be exploited to degrade service availability for other users, creating a cascading effect that compromises the overall integrity of the virtualization platform. The attack vector is particularly dangerous because it requires minimal privileges from the guest perspective, making it accessible to any user with access to the guest operating system.
The mitigation strategies for CVE-2019-17351 primarily involve upgrading to Linux kernel version 5.2.3 or later, which contains the necessary patches to address the resource management issues in the balloon driver. System administrators should also implement monitoring solutions to detect unusual memory mapping patterns that might indicate exploitation attempts. Additionally, implementing resource quotas and limits for guest operating systems can provide an additional layer of protection against excessive resource consumption. Organizations should also consider applying the specific patches provided by their Linux distribution vendors and conducting thorough testing to ensure that the patches do not introduce compatibility issues with existing virtualized workloads. The remediation process should be prioritized based on the criticality of the virtualized environments and the potential impact of resource exhaustion attacks on business operations. This vulnerability demonstrates the importance of proper resource management in hypervisor components and aligns with ATT&CK technique T1499 which covers resource exhaustion attacks against cloud and virtualized environments.