CVE-2021-33959

HIGHNVD 7.57.5—Elevated

7.5

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

CVSS v3: 7.5
EG Score: 7.5(medium)
EPSS: 90.7%
KEV: Not listed

Published

January 18, 2023

Last Modified

April 4, 2025

References (4)

cve@mitrehttps://github.com/lixiang957/CVE-2021-33959
cve@mitrehttps://www.freebuf.com/articles/web/260338.html
af854a3a-2127-422b-91ae-364da2661108https://github.com/lixiang957/CVE-2021-33959
af854a3a-2127-422b-91ae-364da2661108https://www.freebuf.com/articles/web/260338.html

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 18× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-06-02 20:11 UTCepss_batch
2026-06-02 20:11 UTCepss_batch
2026-06-01 13:50 UTCepss_batch
2026-06-01 13:50 UTCepss_batch
2026-05-31 22:29 UTCepss_batch
2026-05-31 22:29 UTCepss_batch
2026-05-31 00:15 UTCepss_batch
2026-05-31 00:15 UTCepss_batch
2026-05-29 13:42 UTCepss_batch
2026-05-29 13:42 UTCepss_batch
2026-05-28 13:43 UTCepss_batch
2026-05-28 13:43 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-25 08:22 UTCEG score recompute
2026-05-25 08:22 UTCGHSA enrichment

Frequently asked(5)

What is CVE-2021-33959?

CVE-2021-33959 is a high vulnerability published on January 18, 2023. Plex media server 1.21 and before is vulnerable to ddos reflection attack via plex service.

When was CVE-2021-33959 disclosed?

CVE-2021-33959 was first published in the National Vulnerability Database on January 18, 2023, with the most recent update on April 4, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-33959 actively exploited?

CVE-2021-33959 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 90.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-33959?

CVE-2021-33959 has a CVSS v3 base score of 7.5 (NVD).

How do I remediate CVE-2021-33959?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-33959, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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CVE-2021-33959

📅 Published

🔄 Last Modified

🔗 References (4)

Weakness Classification(2)

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-33959?

🔗 Related CVEs(same CWE)

Same CWE

Published

Last Modified

References (4)

Frequently asked(5)

Related CVEs(same CWE)