CVE-2026-44838

Description

RabbitMQ is a messaging and streaming broker. From 4.2.0 to before 4.2.4, RabbitMQ's MQTT plugin allows for topic-level authorization using regular expressions with variable substitution. Administrators can create patterns such as ^{client_id}-sensors$ to restrict user access to topics that include their client ID. However, the client_id is provided by the user in the MQTT CONNECT packet and is inserted into the regex pattern without escaping special regex characters. This flaw enables an authenticated MQTT user to inject regex operators to bypass authorization. This vulnerability is fixed in 4.2.4 and 4.3.0.

How to fix CVE-2026-44838

To remediate CVE-2026-44838, upgrade the affected package to a fixed version below.

• —upgrade to 4.2.4 or later

Is CVE-2026-44838 being exploited?

Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.

Affected packages (1)

• >= 4.2.0, < 4.2.4

CVSS scores

References (2)

• WEBgithub.com/rabbitmq/rabbitmq-server/security/advisories/GHSA-x866-xp2g-cx8v
• WEBnvd.nist.gov/vuln/detail/CVE-2026-44838