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Media Server CVE-2021-42835

HIGH
Time-of-check Time-of-use (TOCTOU) Race Condition (CWE-367)
2021-12-08 cve@mitre.org
RCE Media Server Plex
7.0
CVSS 3.1 · NVD
View

Vulnerability Assessment

Weakness
CWE
CWE-367
ASVS 5.0
V15 - Secure Coding and Architecture TOCTOU prevention
Impact

CVSS score of 7.0 (HIGH). Attack characteristics: local attack vector, high complexity, low privileges required, no user interaction not required. Public proof-of-concept exploit code is available.
Exploit ScenarioDerived

Successful exploitation could compromise the high-severity affected system.
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
No patch listed yet 1.2% exploitation probability (EPSS)

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AnalysisAI

An issue was discovered in Plex Media Server through 1.24.4.5081-e362dc1ee. Rated high severity (CVSS 7.0). Public exploit code available and no vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

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Technical ContextAI · show details

This vulnerability is classified under CWE-367. 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). Affected products include: Plex Media Server. Version information: through 1.24.4.5081.

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Severity by source

NVD PRIMARY 7.0 HIGH
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Local
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

DescriptionNVD

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).

Threat Intelligence Overview

EPSS Score
1.2%
Top 36% exploitable
Exploit
POC
Public exploit code exists
Data Quality
2 sources
Confidence: Low
NVD CVE.org EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC Yes
EPSS 1.2%
Patch available No
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
Poc
System Exposure· derived
Small
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

56
Low Medium High Critical
KEV: 0
EPSS: +1
CVSS: +35
PoC: +20
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Remote Code Execution CRITICAL

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.

Affected Products (CPE)NVD

cpe:2.3:a:plex:media_server:*:*:*:*:*:*:*:*

More in Media Server

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CVE-2026-96656 HIGH POC
8.6 Sep 23

Authenticated code execution in Plex Media Server before 1.43.3.10861 is a genuine but privilege-gated code-execution fl
CVE-2026-96654 MEDIUM POC
6.9 Sep 23

Improper neutralization of URL values in Plex Media Server's 'searchOne' parameter allows a remote attacker to invoke ot
CVE-2017-6427 HIGH POC
7.5 Mar 10

A Buffer Overflow was discovered in EvoStream Media Server 1.7.1. Rated high severity (CVSS 7.5), this vulnerability is

CVE-2026-96655 MEDIUM POC
5.3 Sep 23

Server-side request forgery in Plex Media Server before 1.43.3.10861 allows any authenticated user - including a low-tru
CVE-2026-96652 MEDIUM POC
5.3 Sep 23

Server-side request forgery in Plex Media Server before 1.43.3.10861 allows a low-privileged, token-bearing caller to fo
CVE-2020-5741 HIGH POC
7.2 May 08

Deserialization of Untrusted Data in Plex Media Server on Windows allows a remote, authenticated attacker to execute arb
CVE-2018-13415 CRITICAL POC
9.8 Aug 13

In Plex Media Server 1.13.2.5154, the XML parsing engine for SSDP/UPnP functionality is vulnerable to an XML External En
CVE-2020-5742 HIGH POC
8.8 Jun 15

Improper Access Control in Plex Media Server prior to June 15, 2020 allows any origin to execute cross-origin applicatio
CVE-2014-9304 HIGH POC
7.5 Dec 07

Plex Media Server before 0.9.9.3 allows remote attackers to bypass the web server whitelist, conduct SSRF attacks, and e
CVE-2014-9181 MEDIUM POC
5.0 Dec 02

Multiple directory traversal vulnerabilities in Plex Media Server before 0.9.9.3 allow remote attackers to read arbitrar
CVE-2020-5740 HIGH POC
7.8 Apr 22

Improper Input Validation in Plex Media Server on Windows allows a local, unauthenticated attacker to execute arbitrary

CVE-2024-24262 HIGH POC
7.5 Feb 05

media-server v1.0.0 was discovered to contain a Use-After-Free (UAF) vulnerability via the sip_uac_stop_timer function a

Same weakness CWE-367 – Time-of-check Time-of-use (TOCTOU) Race Condition

View all
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CVE-2025-38352 HIGH POC
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CVE-2022-48618 HIGH
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CVE-2023-38146 HIGH POC
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CVE-2025-34027 CRITICAL POC
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CVE-2020-1337 HIGH POC
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Same technique RCE

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CVE-2021-44228 CRITICAL POC
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CVE-2017-7269 CRITICAL POC
9.8
CVE-2022-47966 CRITICAL POC
9.8
CVE-2012-4681 CRITICAL POC
9.8
CVE-2023-3519 CRITICAL POC
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CVE-2015-5119 CRITICAL POC
9.8
CVE-2016-4117 CRITICAL POC
9.8
CVE-2015-3113 CRITICAL POC
9.8

References

Advisories & patches
ADVISORY https://forums.plex.tv/t/security-regarding-cve-2021-42835/761510 ADVISORY https://www.plex.tv/media-server-downloads/ REF https://bugsec.com/experts_teams/

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