Executive Summary

Boxlite is a sandbox service that allows users to run untrusted code inside lightweight virtual machines called Boxes. In versions 0.8.2 and earlier, Boxlite lets users set a timeout for services running inside these virtual machines. When the timeout is reached, Boxlite is supposed to kill the process to stop it. However, instead of using the uncatchable SIGKILL signal, Boxlite uses the catchable SIGALRM signal. This means malicious code inside the sandbox can catch the signal and avoid being killed, allowing it to keep running even after the timeout.

As a result, the malicious code can continue consuming resources inside the virtual machine, leading to resource exhaustion and potentially affecting the availability of the Boxlite service.

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Impact Analysis

This vulnerability can allow malicious code running inside the Boxlite sandbox to evade termination after a timeout, causing it to continue consuming system resources.

The continued resource consumption can lead to resource exhaustion within the virtual machine, which may degrade or disrupt the availability of the Boxlite service.

This can impact system stability and availability, potentially affecting other services or users relying on Boxlite.

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Mitigation Strategies

To mitigate this vulnerability, you should update Boxlite to a version that includes the patch applied via commit 28159fc. This patch changes the signal used to terminate timed-out processes from the catchable SIGALRM to the uncatchable SIGKILL, preventing malicious code from continuing to run after the timeout.

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