CVE-2026-96656: high-severity vulnerability in Plex Media Server
Plex Media Server arbitrary file write
Published · Updated
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Patch now. It under exploitation confirmed by CISA and has a working public exploit.
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.
A flaw in Plex Media Server lets someone with administrator access write files that the server may later run automatically. This could let an attacker take deeper control of the server.
Plex Media Server before 1.43.3.10861 (CWE-73, CVSS 8.6) passes the TranscoderH264Options preference verbatim into the x264 option string on every transcode, allowing an authenticated admin to write arbitrary files. At startup, all .so files are loaded without signature, execute-bit, or symbol validation, so attacker-written files may be executed on load. Preconditions are administrator privileges on the server; impact is arbitrary file write leading to code execution.
In the same product, most dangerous first.