CriticalCVE-2026-96656

    Plex Media Server arbitrary file write (CVE-2026-96656)

    Published Last modified In CISA KEV since Sources: pwn.watch, CVE.org

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    What is affected, what to do

    Plex Media Server before 1.43.3.10861 allows an admin user to write arbitrary files that may be executed on load. The preference TranscoderH264Options is appended verbatim to x264's option string on every transcode.

    The vulnerability is being actively exploited; treat it as a priority. Update Plex Media Server to version 1.43.3.10861. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Plex Media Server lt *..1.43.3.10861
    Fixed in
    • Plex Media Server 1.43.3.10861

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    8.6

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: Vendor (CNA), CVSS v4

    7.2

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: pwn.watch, CVE.org

    1.8 %

    EPSS score

    Moderate — model estimates 1-10% exploitation likelihood.

    Source: FIRST EPSS, percentile 78.5

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    219.06 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploitedSource: VulnCheck KEV (opens in a new tab) How we classify
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    8.6 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    7.2
    CVSS v4

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    8.6
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    1.8 %
    Moderate — model estimates 1-10% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    78.5
    High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · not automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 19 October 2026
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-73

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This CVE sits on KEV because it chains with CVE-2026-96652/96654/96655 into a documented full exploitation chain that converts an authenticated-admin flaw into a reliable code-execution primitive inside the transcoder process. CISA has not flagged ransomware use, the statistical exploitation likelihood is modest, and the CVSS vector requires admin privileges. Treat it as high priority when Plex instances are internet-reachable or when admin credentials live outside strong IAM controls; treat it as medium priority for strictly internal deployments behind VPN and MFA. Relevant for NIS2/KRITIS scope whenever Plex runs on hosts that also carry other services or offer a pivot into office or OT networks.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Upgrade Plex Media Server to 1.43.3.10861 or later immediately — the vendor patch fixes the handling of the TranscoderH264Options preference and the unchecked loading of .so files at startup.
      • Inventory all Plex admin accounts, enforce MFA and rotate weak or reused passwords; exploitation requires valid or compromised admin credentials (PR:H).
      • Remove the web admin interface (default TCP/32400) from internet exposure: place it behind a reverse proxy, VPN, or firewall rule deny any -> any:32400 from untrusted zones. Allow only internal management networks.
      • Audit the Plex installation and transcoder/plugin directories for unexpected .so files, modified mtimes, and new preference entries (Preferences.xml, key TranscoderH264Options). Capture suspicious files forensically before deletion.
      • If patching must be delayed: run the Plex service under a dedicated unprivileged service account and constrain plugin-path read/write via AppArmor, SELinux, or equivalent MAC.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: isolate the media server in its own VLAN with egress filtering; restrict outbound traffic to Plex update and metadata endpoints only, to kill C2 channels from any loaded malicious .so.
      • Filesystem hardening: mount plugin and codec directories (/var/lib/plexmediaserver/, Resources/Codecs/, Library/Application Support/Plex Media Server/) with noexec where technically feasible, or monitor them with file-integrity tooling (AIDE, Tripwire, Wazuh FIM).
      • IAM hardening: shrink the admin role to the strict minimum, abolish shared admin accounts, shorten session timeouts. Audit plex.tv account linkages and remove unused ones.
      • WAF / reverse-proxy rule in front of Plex: block or at minimum alert on PUT/POST requests to /:/prefs that carry a TranscoderH264Options parameter, and on uploads with a .so extension.
      • EDR / HIDS policy that prevents the Plex process (Plex Media Server, Plex Transcoder) from loading unsigned shared libraries, or that reports unknown dlopen() calls.
      • Back up the current Preferences.xml and plugin directories before patching, so any pre-existing compromise remains reconstructable during post-audit.

    3. Runbook step 3

      Detection rules

      • Linux auditd / Sysmon for Linux: file-create events for *.so under the Plex codec/plugin paths with writer process Plex Media Server or Plex Transcoder. Sigma shape: category: file_event + TargetFilename endswith: '.so' + TargetFilename contains: 'Plex'.
      • Process telemetry: Plex Transcoder as parent of unexpected children (sh, bash, curl, wget, nc, python) — the classic post-exploitation signal after a successful .so load.
      • Web/reverse-proxy access logs: HTTP requests to /:/prefs carrying a TranscoderH264Options= parameter, especially with shell metacharacters (;, |, `, $() or path fragments.
      • KQL (Defender for Endpoint) example: DeviceFileEvents | where FolderPath has "Plex Media Server" and FileName endswith ".so" | where InitiatingProcessFileName in ("Plex Media Server","Plex Transcoder").
      • Network (Zeek/Suricata): new outbound connections from the Plex host to non-Plex infrastructure immediately after a transcode event; maintain a baseline of legitimate Plex FQDNs.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    Plex Media Server before 1.43.3.10861 allows an admin user to write arbitrary files that may be executed on load. The preference TranscoderH264Options is appended verbatim to x264's option string on every transcode. At startup, all .so files are run without signature, execute bit, or symbol checks.

    Source: pwn.watch, cvelistv5, NVD (NIST), CISA KEV Catalog

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    PlexMedia Server
    • < 1.43.3.10861
    • 1.43.3.10861
    plexmedia_server
    • < 1.43.3.10861
    • 1.43.3.10861

    Vendors and products

    Weakness classes (CWE)

    • CWE-73External Control of File Name or Path

      Base

      The product allows user input to control or influence paths or file names that are used in filesystem operations.

      Entry at MITRE CWE-73

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited

    References & sources

    • forums.plex.tvurlRelease notes, Release notes
    • CVE.org (MITRE)urlVulnerability database, Third-party advisory, Vulnerability database
    • raw.githubusercontent.comurlThird-party advisory, Third-party advisory
    • zmain.infourlThird-party advisory, Third-party advisory
    • boredhackerblog.info2026/10/plex-vulnerabilities-being-exploited-in.htmlThird-party advisory, Third-party advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2026-96656government-resource, US government resource
    • pwn.watchpwn.watch: Plex2Shell: chained Plex Media Server RCE exploited for minerspwn-watch
    • bleepingcomputer.comCISA / BleepingComputer: Plex2Shell actively exploitedpwn-watch
    • forums.plex.tvPlex forum: Important Security Updatepwn-watch
    • CVE.org (MITRE)CVE-2026-96652pwn-watch
    • qnap.comQNAP Security Notice: Plex Media Server Vulnerabilities (Plex2Shell) – Update to 1.43.3.10861 or Later Immediatelypwn-watch
    • bleepingcomputer.comQNAP says hackers breaching NAS devices in Plex2Shell attackspwn-watch

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. NVD analysis modifiedNVD

      Product mapping changed:
      Show 3 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationchanged
      OR *cpe:2.3:a:plex:media_server:*:*:*:*:*:*:*:* versions up to (excluding) 1.43.0.10861
      OR *cpe:2.3:a:plex:media_server:*:*:*:*:*:*:*:* versions up to (excluding) 1.43.3.10861
      Reference typeadded
      —
      CISA-ADP: https://www.boredhackerblog.info/2026/10/plex-vulnerabilities-being-exploited-in.html Types: Third Party Advisory
      Reference typeadded
      —
      CISA-ADP: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-96656 Types: US Government Resource

      Source identifier: nvd@nist.gov

    2. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: active, automatable: no

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentremoved
      {"id":"CVE-2026-96656","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-20T19:46:34.862476Z"}
      —
      SSVC assessmentadded
      —
      {"id":"CVE-2026-96656","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-19T00:00:00+00:00"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    3. CISA KEV entry updated9119a7d8…

      4 individual changes: Date Added, Due Date, Required Action, Vulnerability Name

      Show 4 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Date Addedadded
      —
      2026-10-20
      Due Dateadded
      —
      2026-10-20
      Required Actionadded
      —
      2026-10-20
      Vulnerability Nameadded
      —
      2026-10-20

      Source identifier: 9119a7d8-5eab-497f-8521-727c672e3725

    4. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: active, automatable: no

      Show 4 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://www.boredhackerblog.info/2026/10/plex-vulnerabilities-being-exploited-in.html
      Referenceadded
      —
      https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-96656
      SSVC assessmentremoved
      {"id":"CVE-2026-96656","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-19T00:00:00+00:00"}
      —
      SSVC assessmentadded
      —
      {"id":"CVE-2026-96656","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-20T19:46:34.862476Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    5. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentremoved
      {"id":"CVE-2026-96656","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-09-23T16:35:05.105006Z"}
      —
      SSVC assessmentadded
      —
      {"id":"CVE-2026-96656","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-19T00:00:00+00:00"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Show 3 older changes

    1. Initial analysis by NVDNVD

      Newly listed as affected:
      Show 5 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationadded
      —
      OR *cpe:2.3:a:plex:media_server:*:*:*:*:*:*:*:* versions up to (excluding) 1.43.0.10861
      Reference typeadded
      —
      Cybersecurity and Infrastructure Security Agency (CISA) U.S. Civilian Government: https://forums.plex.tv/t/plex-media-server/30447/711 Types: Release Notes
      Reference typeadded
      —
      Cybersecurity and Infrastructure Security Agency (CISA) U.S. Civilian Government: https://raw.githubusercontent.com/cisagov/CSAF/develop/csaf_files/IT/white/2026/va-26-266-01.json Types: Third Party Advisory
      Reference typeadded
      —
      Cybersecurity and Infrastructure Security Agency (CISA) U.S. Civilian Government: https://www.cve.org/CVERecord?id=CVE-2026-96656 Types: Third Party Advisory, VDB Entry
      Reference typeadded
      —
      Cybersecurity and Infrastructure Security Agency (CISA) U.S. Civilian Government: https://zmain.info/blog/plex2shell Types: Third Party Advisory

      Source identifier: nvd@nist.gov

    2. Received9119a7d8…

      CVSS V4.0: AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

      CVSS V3.1: AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Weakness type: CWE-73

      Description added or changed

      Show 10 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionadded
      —
      Plex Media Server before 1.43.3.10861 allows an admin user to write arbitrary files that may be executed on load. The preference TranscoderH264Options is appended verbatim to x264's option string on every transcode. At startup, all .so files are run without signature, execute bit, or symbol checks.
      CVSSadded
      —
      AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
      CVSSadded
      —
      AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
      Weakness type (CWE)added
      —
      CWE-73
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/96xxx/CVE-2026-96656.json">CVE-2026-96656</a>
      Referenceadded
      —
      https://forums.plex.tv/t/plex-media-server/30447/711
      Referenceadded
      —
      https://raw.githubusercontent.com/cisagov/CSAF/develop/csaf_files/IT/white/2026/va-26-266-01.json
      Referenceadded
      —
      https://www.cve.org/CVERecord?id=CVE-2026-96656
      Referenceadded
      —
      https://zmain.info/blog/plex2shell
      SSVC assessmentadded
      —
      {"id":"CVE-2026-96656","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-09-14T18:24:56.053053Z"}

      Source identifier: 9119a7d8-5eab-497f-8521-727c672e3725

    3. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-96656","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-09-23T16:35:05.105006Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

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