CVE-2021-42835 : What You Need to Know

An issue in Plex Media Server allows an attacker to execute code through a TOCTOU race condition. The vulnerability affects versions up to 1.24.4.5081-e362dc1ee.

Understanding CVE-2021-42835

What is CVE-2021-42835?

The vulnerability in Plex Media Server allows an attacker with low-privileged access to execute code via the exposed RPC service, leading to potential code execution.

The Impact of CVE-2021-42835

The vulnerability enables an attacker to interact with RPC functionality and execute arbitrary code, potentially leading to a system compromise. The code runs with SYSTEM privileges within the Plex update service context.

Technical Details of CVE-2021-42835

Vulnerability Description

The issue arises from a TOCTOU race condition in the update service component of Plex Media Server, enabling unauthorized code execution.

Affected Systems and Versions

Vulnerable versions include all releases up to 1.24.4.5081-e362dc1ee.

Exploitation Mechanism

Attackers can leverage the exposed RPC service to execute code locally or remotely via SMB, manipulating the RPC functionality through a race condition.

Mitigation and Prevention

Immediate Steps to Take

Update Plex Media Server to the latest version to patch the vulnerability.
Restrict network access to the RPC service to limit exposure.

Long-Term Security Practices

Regularly monitor for security updates and apply patches promptly.
Employ the principle of least privilege to restrict access rights.

Patching and Updates

Stay informed about security advisories from Plex and apply updates as soon as they are available.