CVE-2021-33818

Name: CVE-2021-33818
Creator: NVD / NIST
Published: 2021-06-18T19:15:07.497+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 1.93%

Last modified Jun 17, 2026

CVE-2021-33818 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. An issue was discovered in UniFi Protect G3 FLEX Camera Version UVC.v4.30.0.67. Attackers can use slowhttptest tool to send incomplete HTTP request, which could make server keep waiting for the packet to finish the connection, until its resource exhausted. EPSS estimates a 1.93% chance of exploitation in the next 30 days.

Description

An issue was discovered in UniFi Protect G3 FLEX Camera Version UVC.v4.30.0.67. Attackers can use slowhttptest tool to send incomplete HTTP request, which could make server keep waiting for the packet to finish the connection, until its resource exhausted. Then the web server is denial-of-service.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

1.93%

77.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-400

Affected Software

Vendor	Product	Versions
Ui	Camera G3 Flex Firmware	uvc.v4.30.0.67

References

https://github.com/Jian-Xian/CVE-POC/blob/master/CVE-2021-33818.mdExploit, Third Party Advisory
https://github.com/shekyan/slowhttptestThird Party Advisory
https://store.ui.com/collections/unifi-protect-cameras/products/unifi-video-g3-flex-cameraProduct, Vendor Advisory
https://github.com/Jian-Xian/CVE-POC/blob/master/CVE-2021-33818.mdExploit, Third Party Advisory
https://github.com/shekyan/slowhttptestThird Party Advisory
https://store.ui.com/collections/unifi-protect-cameras/products/unifi-video-g3-flex-cameraProduct, Vendor Advisory

Timeline

Published: Jun 18, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-33818?

How severe is CVE-2021-33818?

CVE-2021-33818 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 1.93% probability of exploitation in the next 30 days.

How do I fix CVE-2021-33818?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-33818?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST