CVE-2021-33820

HIGHNVD 7.57.5—

7.5

An issue was discovered in UniFi Protect G3 FLEX Camera Version UVC.v4.30.0.67.Attacker could send a huge amount of TCP SYN packet to make web service's resource exhausted. Then the web server is denial-of-service.

CVSS v3: 7.5
EG Score: 7.5(medium)
EPSS: 68.6%
KEV: Not listed

Published

June 18, 2021

Last Modified

November 21, 2024

References (6)

cve@mitrehttps://github.com/Jian-Xian/CVE-POC/blob/master/CVE-2021-33820.md
cve@mitrehttps://linuxhint.com/hping3/
cve@mitrehttps://store.ui.com/collections/unifi-protect-cameras/products/unifi-video-g3-flex-camera
af854a3a-2127-422b-91ae-364da2661108https://github.com/Jian-Xian/CVE-POC/blob/master/CVE-2021-33820.md
af854a3a-2127-422b-91ae-364da2661108https://linuxhint.com/hping3/
af854a3a-2127-422b-91ae-364da2661108https://store.ui.com/collections/unifi-protect-cameras/products/unifi-video-g3-flex-camera

Weakness Classification(1)

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

CWE-400Uncontrolled Resource Consumption (Denial of Service)

Data Freshness Timeline

(refreshed 12× in last 7d / 20× 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.

2026-06-04 13:10 UTCepss_batch
2026-06-04 13:10 UTCepss_batch
2026-06-02 20:11 UTCepss_batch
2026-06-02 20:11 UTCepss_batch
2026-06-01 13:50 UTCepss_batch
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2026-05-31 22:29 UTCepss_batch
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2026-05-31 00:15 UTCepss_batch
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2026-05-29 13:42 UTCepss_batch
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2026-05-28 13:43 UTCepss_batch
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2026-05-27 13:39 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-26 14:45 UTCEG score recompute
2026-05-26 14:45 UTCGHSA enrichment
2026-05-26 13:42 UTCepss_batch

Frequently asked(5)

What is CVE-2021-33820?

CVE-2021-33820 is a high vulnerability published on June 18, 2021. An issue was discovered in UniFi Protect G3 FLEX Camera Version UVC.v4.30.0.67.Attacker could send a huge amount of TCP SYN packet to make web service's resource exhausted. Then the web server is denial-of-service.

When was CVE-2021-33820 disclosed?

CVE-2021-33820 was first published in the National Vulnerability Database on June 18, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-33820 actively exploited?

CVE-2021-33820 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 68.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-33820?

CVE-2021-33820 has a CVSS v3 base score of 7.5 (NVD).

How do I remediate CVE-2021-33820?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-33820, 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-2021-33820

📅 Published

🔄 Last Modified

🔗 References (6)

Weakness Classification(1)

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-33820?

🔗 Related CVEs(same CWE)

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Published

Last Modified

References (6)

Frequently asked(5)

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