CVE-2021-34431

Name: CVE-2021-34431
Creator: NVD / NIST
Published: 2021-07-22T14:15:08.05+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 1.11%

Last modified Jun 17, 2026

CVE-2021-34431 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. In Eclipse Mosquitto version 1.6 to 2.0.10, if an authenticated client that had connected with MQTT v5 sent a crafted CONNECT message to the broker a memory leak would occur, which could be used to provide a DoS attack against the broker.. EPSS estimates a 1.11% chance of exploitation in the next 30 days.

Description

In Eclipse Mosquitto version 1.6 to 2.0.10, if an authenticated client that had connected with MQTT v5 sent a crafted CONNECT message to the broker a memory leak would occur, which could be used to provide a DoS attack against the broker.

Metrics

CVSS 3.1

6.5/10

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

EPSS Probability

1.11%

61.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Eclipse	Mosquitto	>= 1.6, <= 2.0.10

References

https://bugs.eclipse.org/bugs/show_bug.cgi?id=573191Mailing List, Vendor Advisory
https://bugs.eclipse.org/bugs/show_bug.cgi?id=573191Mailing List, Vendor Advisory

Timeline

Published: Jul 22, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-34431?

How severe is CVE-2021-34431?

CVE-2021-34431 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 1.11% probability of exploitation in the next 30 days.

How do I fix CVE-2021-34431?

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-2021-34431?

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

Scan your code now

Source: NVD / NIST