CVE-2026-44838 rabbitmq CVE debrief

Who should care

Organizations running RabbitMQ 4.2.0-4.2.3 with MQTT plugin enabled and topic-level authorization configured using client_id-based patterns. DevOps teams managing message broker infrastructure, security teams monitoring messaging system access controls, and application teams building IoT or event-driven architectures on RabbitMQ MQTT.

Technical summary

The RabbitMQ MQTT plugin supports topic-level authorization using configurable regex patterns with variable substitution. Administrators can define patterns such as ^{client_id}-sensors$ to restrict users to topics containing their own client identifier. The vulnerability arises because the client_id value, provided by the connecting user in the MQTT CONNECT packet, is inserted directly into the regex pattern without escaping regex special characters (e.g., ., *, +, ?, ^, $, [, ], (, ), {, }, |, ). This allows an authenticated attacker to inject regex operators into their client_id, causing the authorization pattern to match unintended topics and bypass access controls. The attack requires valid MQTT credentials but no additional privileges. Successful exploitation grants unauthorized publish/subscribe access to topics that should be restricted.

Defensive priority

medium

Recommended defensive actions

• Upgrade RabbitMQ to version 4.2.4 or 4.3.0 or later to remediate this vulnerability
• Review MQTT plugin authorization configurations for patterns using client_id variable substitution
• Audit topic access logs for unauthorized access attempts using crafted client_id values
• Consider implementing additional authorization layers independent of regex-based pattern matching until patching is complete

Evidence notes

Vulnerability confirmed through official GitHub Security Advisory GHSA-x866-xp2g-cx8v. Affected versions explicitly stated as 4.2.0 to before 4.2.4. Fix versions confirmed as 4.2.4 and 4.3.0. CVSS 4.0 vector provided in NVD source data.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.