How severe is CVE-2021-42835?

CVE-2021-42835 has a CVSS 3.x base score of 7.0, rated high severity. It is exploitable over local access with high attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-42835 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (64th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-42835?

CVE-2021-42835 affects Plex Media Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-42835?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-42835 published?

CVE-2021-42835 was published on 2021-12-08 and last updated on 2026-06-17.

CVE-2021-42835

CVE-2021-42835 is a high-severity vulnerability in Plex Media Server with a CVSS 3.x base score of 7.0. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-367.

Key facts

Severity: High (CVSS 3.x base score 7.0)
CVSS v2: 6.9
EPSS exploit prediction: 1% (64th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-367
Affected product: Plex Media Server
Published: 2021-12-08
Last modified: 2026-06-17

Description

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).

Frequently asked questions

What is CVE-2021-42835?: 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).
How severe is CVE-2021-42835?: CVE-2021-42835 has a CVSS 3.x base score of 7.0, rated high severity. It is exploitable over local access with high attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-42835 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (64th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-42835?: CVE-2021-42835 affects Plex Media Server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-42835?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-42835 published?: CVE-2021-42835 was published on 2021-12-08 and last updated on 2026-06-17.

References

Affected products (1)

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

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