An issue was discovered in Plex Media Server through 1.24.4.5081-e362dc1ee. An attacker (with a foothold in a endpoint via a low-privileged user account) can access the exposed RPC service of the update service component. This RPC functionality allows the attacker to interact with the RPC functionality and execute code from a path of his choice (local, or remote via SMB) because of a TOCTOU race condition. This code execution is in the context of the Plex update service (which runs as SYSTEM).

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-42835
• https://bugsec.com/experts_teams/
• https://forums.plex.tv/t/security-regarding-cve-2021-42835/761510
• https://ir-on.io/2021/12/02/local-privilege-plexcalation/
• https://www.plex.tv/media-server-downloads/