How severe is CVE-2021-33959?

CVE-2021-33959 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-33959 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 15% (96th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-33959?

CVE-2021-33959 affects Plex Media Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-33959?

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-2021-33959 published?

CVE-2021-33959 was published on 2023-01-18 and last updated on 2026-06-17.

CVE-2021-33959

CVE-2021-33959 is a high-severity vulnerability in Plex Media Server with a CVSS 3.x base score of 7.5. Its EPSS exploit-prediction score of 15% places it in the 96th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-346.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 15% (96th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-346
Affected product: Plex Media Server
Published: 2023-01-18
Last modified: 2026-06-17

Description

Plex media server 1.21 and before is vulnerable to ddos reflection attack via plex service.

Frequently asked questions

What is CVE-2021-33959?: Plex media server 1.21 and before is vulnerable to ddos reflection attack via plex service.
How severe is CVE-2021-33959?: CVE-2021-33959 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-33959 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 15% (96th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-33959?: CVE-2021-33959 affects Plex Media Server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-33959?: 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-2021-33959 published?: CVE-2021-33959 was published on 2023-01-18 and last updated on 2026-06-17.

References

Affected products (1)

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

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