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Vulnerability record · CVE-2021-34431 · published 22 July 2021

CVE-2021-34431: Eclipse mosquitto memory leak vulnerability

Eclipse · Mosquitto

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.

6.5 CVSS 3.1 Medium EPSS 1.1% · top 35.4% CWE-401 · Memory leak
6.5CVSS 3.1 base score, v2 4.0
1.1%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References
17 Jun 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://bugs.eclipse.org/bugs/show_bug.cgi?id=573191 Mailing ListVendor Advisory
https://bugs.eclipse.org/bugs/show_bug.cgi?id=573191 Mailing ListVendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

8.1CVE-2018-12550Eclipse mosquitto vulnerabilityWhen Eclipse Mosquitto version 1.0 to 1.5.5 (inclusive) is configured to use an ACL file, and that ACL file is empty, or contains only comments or bl…EPSS 1.4%8.1CVE-2018-12551Eclipse mosquitto improper authentication vulnerabilityWhen Eclipse Mosquitto version 1.0 to 1.5.5 (inclusive) is configured to use a password file for authentication, any malformed data in the password f…EPSS 1.5%7.5CVE-2023-5632Eclipse mosquitto vulnerabilityIn Eclipse Mosquito before and including 2.0.5, establishing a connection to the mosquitto server without sending data causes the EPOLLOUT event to b…EPSS 0.69%7.5CVE-2023-3592Eclipse mosquitto memory leak vulnerabilityIn Mosquitto before 2.0.16, a memory leak occurs when clients send v5 CONNECT packets with a will message that contains invalid property types.EPSS 0.79%7.5CVE-2023-28366Eclipse mosquitto memory leak vulnerabilityThe broker in Eclipse Mosquitto 1.3.2 through 2.x before 2.0.16 has a memory leak that can be abused remotely when a client sends many QoS 2 messages…EPSS 1.3%7.5CVE-2021-41039Eclipse mosquitto vulnerabilityIn versions 1.6 to 2.0.11 of Eclipse Mosquitto, an MQTT v5 client connecting with a large number of user-property properties could cause excessive CP…EPSS 1.4%7.5CVE-2021-34432Eclipse mosquitto improper input validation vulnerabilityIn Eclipse Mosquitto versions 2.0.7 and earlier, the server will crash if the client tries to send a PUBLISH packet with topic length = 0.EPSS 1.2%7.5CVE-2017-7655Eclipse mosquitto null pointer dereference vulnerabilityIn Eclipse Mosquitto version from 1.0 to 1.4.15, a Null Dereference vulnerability was found in the Mosquitto library which could lead to crashes for …EPSS 1.8%

Source: NIST National Vulnerability Database (record CVE-2021-34431), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.