Plex Media Server Improper Neutralization of Encoded URI Schemes in a Web Page Vulnerability

What it is

Plex Media Server contains an improper neutralization of encoded URI schemes in a web page vulnerability that could allow an attacker to call other plugins' functions and supply their own parameters. This vulnerability can be chained with CVE-2026-96652, CVE-2026-96655, and CVE-2026-96656.

Who's affected

Anyone using Plex Media Server.

Under attack?

Yes. CISA added this to its catalog of actively exploited vulnerabilities on Oct 20, 2026.

What to do

Install the vendor's security update. If there isn't one yet, apply the vendor's workaround, or stop using the product until it's fixed. CISA lists this as actively exploited, so treat it as urgent.

Fixed in

See the vendor's advisory

CISA deadline

Federal agencies must fix this by Oct 23, 2026. Everyone else should treat that as a ceiling, not a target.

CISA's instruction

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.