CVE-2019-3900 in SD-WAN Edge
Summary
by MITRE
An infinite loop issue was found in the vhost_net kernel module in Linux Kernel up to and including v5.1-rc6, while handling incoming packets in handle_rx(). It could occur if one end sends packets faster than the other end can process them. A guest user, maybe remote one, could use this flaw to stall the vhost_net kernel thread, resulting in a DoS scenario.
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Analysis
by VulDB Data Team • 06/27/2024
The vulnerability identified as CVE-2019-3900 represents a critical denial of service weakness within the Linux kernel's virtualization infrastructure, specifically affecting the vhost_net module that facilitates high-performance network virtualization in virtualized environments. This flaw manifests as an infinite loop condition that occurs during packet processing within the handle_rx() function, creating a scenario where legitimate network traffic can be exploited to cause system instability. The vulnerability affects Linux kernel versions up to and including v5.1-rc6, making it particularly concerning for systems running older kernel versions that may not have received the subsequent security patches.
The technical mechanism behind this vulnerability stems from the vhost_net module's handling of asynchronous packet processing in virtualized network environments. When network traffic arrives at a virtualized network interface, the vhost_net module processes incoming packets through the handle_rx() function which manages the reception and processing of network data. The infinite loop occurs when packet flow rates exceed the processing capacity of the receiving end, creating a condition where the kernel thread responsible for handling these packets becomes trapped in an endless processing cycle. This scenario typically arises in virtualized environments where a guest operating system sends network packets at a rate that overwhelms the host system's ability to process them, particularly when the vhost_net module is in use for high-speed network virtualization.
The operational impact of CVE-2019-3900 extends beyond simple system unresponsiveness to create a complete denial of service condition that can affect virtualized infrastructure at scale. Attackers leveraging this vulnerability can potentially cause virtual machines to become unresponsive, leading to service disruption for applications running within those virtual environments. The vulnerability is particularly dangerous in cloud computing and containerized environments where multiple virtual machines share host resources, as a single malicious guest could potentially affect the entire host system's network capabilities. This makes the vulnerability a significant concern for cloud service providers and organizations relying on virtualized infrastructure, as it could be exploited to create widespread service interruptions without requiring elevated privileges on the target system.
The security implications of this vulnerability align with common attack patterns documented in the ATT&CK framework under the "Denial of Service" tactic, where adversaries seek to disrupt system availability by consuming resources or creating conditions that prevent normal operation. From a CWE perspective, this vulnerability maps to CWE-835, which describes the weakness of an infinite loop or infinite recursion that can lead to system resource exhaustion and denial of service conditions. The vulnerability demonstrates how seemingly benign network traffic handling can be exploited to create system instability, highlighting the importance of proper input validation and resource management in kernel-level code. Organizations should implement immediate mitigations including kernel version updates to patched versions, network traffic monitoring to detect anomalous packet patterns, and virtualization environment hardening measures to limit the potential impact of such attacks. The vulnerability also underscores the necessity of regular security assessments and patch management processes to address similar issues in complex virtualized environments where multiple layers of abstraction can introduce unexpected security weaknesses.