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Vulnerability record · CVE-2021-34432 · published 27 July 2021

CVE-2021-34432: Eclipse mosquitto improper input validation vulnerability

Eclipse · Mosquitto

In 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.

7.5 CVSS 3.1 High EPSS 1.2% · top 31.9% CWE-20 · Improper input validation
7.5CVSS 3.1 base score, v2 5.0
1.2%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References, 2 tagged exploit
2 Jul 2026Last modified by NVD

Description

In 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.

CVSS:3.1/AV:N/AC:L/PR:N/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=574141 ExploitIssue TrackingPatchVendor Advisory
https://bugs.eclipse.org/bugs/show_bug.cgi?id=574141 ExploitIssue TrackingPatchVendor 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-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%7.5CVE-2018-20145Eclipse mosquitto incorrect permission assignment vulnerabilityEclipse Mosquitto 1.5.x before 1.5.5 allows ACL bypass: if the option per_listener_settings was set to true, and the default listener was in use, and…EPSS 1.6%

Source: NIST National Vulnerability Database (record CVE-2021-34432), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.