CVE-2021-33820Public exploitNetwork attack vector

Unauthenticated web-service exhaustion via TCP SYN flood

Published Jun 18, 2021 · Updated Aug 3, 2024

Denial-of-service in UniFi Protect G3 FLEX Camera UVC.v4.30.0.67 allows remote attackers to exhaust web-service resources via TCP SYN packets. The camera web server allocates or retains resources while processing a large volume of connection-opening SYN packets, leaving normal requests unserved. The attack requires network reachability to the camera service and causes service interruption without evidence of data disclosure or modification.

CVSS severity7.5
High
EPSS probability1.93%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial-of-service in UniFi Protect G3 FLEX Camera UVC.v4.30.0.67 allows remote attackers to exhaust web-service resources via TCP SYN packets. The camera web server allocates or retains resources while processing a large volume of connection-opening SYN packets, leaving normal requests unserved. The attack requires network reachability to the camera service and causes service interruption without evidence of data disclosure or modification.

The record

CVE
CVE-2021-33820
Published
Jun 18, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1499.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 18, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.0NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1499.002Network Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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