CVE-2019-18683 : Security Advisory and Response

A vulnerability was found in the Linux kernel, specifically in the drivers/media/platform/vivid component, up to version 5.3.8. This vulnerability allows for privilege escalation in certain Linux distributions, but only if local users have access to /dev/video0 and if the driver is loaded. The issue arises due to multiple race conditions that occur when stopping the streaming process in the driver, which is part of the V4L2 subsystem. These race conditions are a result of incorrect mutex locking in the functions vivid_stop_generating_vid_cap(), vivid_stop_generating_vid_out(), sdr_cap_stop_streaming(), and their associated kthreads. At least one of these race conditions results in a use-after-free vulnerability.

Understanding CVE-2019-18683

This section provides an in-depth understanding of the CVE-2019-18683 vulnerability.

What is CVE-2019-18683?

CVE-2019-18683 is a vulnerability found in the Linux kernel's drivers/media/platform/vivid component, allowing for privilege escalation under specific conditions.

The Impact of CVE-2019-18683

The vulnerability can lead to privilege escalation in certain Linux distributions where local users have access to /dev/video0 and the driver is loaded. It stems from race conditions during the streaming stopping process in the V4L2 subsystem.

Technical Details of CVE-2019-18683

This section delves into the technical aspects of CVE-2019-18683.

Vulnerability Description

The vulnerability in drivers/media/platform/vivid in the Linux kernel through version 5.3.8 allows for privilege escalation due to race conditions during the streaming stopping process.

Affected Systems and Versions

Affected Component: drivers/media/platform/vivid
Affected Versions: Up to Linux kernel version 5.3.8

Exploitation Mechanism

The vulnerability is exploited by local users with access to /dev/video0 and a loaded driver, triggering race conditions in vivid_stop_generating_vid_cap(), vivid_stop_generating_vid_out(), sdr_cap_stop_streaming(), and associated kthreads.

Mitigation and Prevention

Learn how to mitigate and prevent the CVE-2019-18683 vulnerability.

Immediate Steps to Take

Restrict access to /dev/video0 to trusted users only
Regularly update the Linux kernel to patched versions

Long-Term Security Practices

Implement the principle of least privilege for user access
Monitor and audit system calls and driver loading activities

Patching and Updates

Apply security patches promptly to the Linux kernel to address the vulnerability