Denial of service in Eclipse Mosquitto

Published: 2021-04-08
Risk Medium
Patch available YES
Number of vulnerabilities 1
CVE ID CVE-2021-28166
Exploitation vector Network
Public exploit N/A
Vulnerable software
Eclipse Mosquitto
Server applications / Other server solutions

Vendor Eclipse

Security Advisory

This security advisory describes one medium risk vulnerability.

1) NULL pointer dereference

Risk: Medium

CVSSv3.1: 5.7 [CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C] [PCI]

CVE-ID: CVE-2021-28166

CWE-ID: CWE-476 - NULL Pointer Dereference

Exploit availability: No


The vulnerability allows a remote user to perform a denial of service (DoS) attack.

The vulnerability exists due to a NULL pointer dereference error in Eclipse Mosquitto when processing CONNACK messages. A remote authenticated user connected with MQTT v5 can send a specially crafted CONNACK message to the broker, trigger a NULL pointer dereference error and crash the service.


Install update from vendor's website.

Vulnerable software versions

Eclipse Mosquitto: 2.0.0, 2.0.1, 2.0.2, 2.0.3, 2.0.4, 2.0.5, 2.0.6, 2.0.7, 2.0.8, 2.0.9

CPE External links

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.