SOC status:Duty analyst on shift

UK Cyber Defence
VulnerabilityModified

CVE-2021-28166

In Eclipse Mosquitto version 2.0.0 to 2.0.9, if an authenticated client that had connected with MQTT v5 sent a crafted CONNACK message to the broker, a NULL pointer dereference would occur.

MEDIUM 6.5EPSS 0.97%

Does this matter?

Lower severity and a low EPSS score (0.97%). Track it; it rarely justifies an emergency change on its own.

Description

In Eclipse Mosquitto version 2.0.0 to 2.0.9, if an authenticated client that had connected with MQTT v5 sent a crafted CONNACK message to the broker, a NULL pointer dereference would occur.

CVSS 3.1
6.5 MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS
0.97% probability · 62th percentile
Public exploits
None in Exploit-DB
CISA KEV
Not listed
Weakness
CWE-476
Affected
eclipse/mosquitto
Source
emo@eclipse.org
EPSS trend
0%3%5%26 October 2026: 0.97%26 October 202626 October 2026

EPSS 1.0% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.