The vulnerability CVE-2026-44838 affects RabbitMQ's MQTT plugin used in Red Hat Hardened Images. It arises because the client ID provided in the MQTT CONNECT packet is inserted into authorization regular expression patterns without proper escaping of special characters. This allows an authenticated MQTT user to inject regex operators and bypass topic-level authorization controls, gaining unauthorized access to topics. Red Hat has issued a security advisory (RHSA-2026:45128) and released updated RPM packages rabbitmq-server4.3-4.3.4-0.1.hum1 for aarch64 and x86_64 architectures to fix this flaw.

An attacker with valid MQTT authentication credentials can exploit this vulnerability to bypass topic-level authorization and access sensitive topics they are not authorized to use. This compromises confidentiality and integrity of MQTT messaging within affected Red Hat Hardened Images environments. There is no indication of impact on availability. No known exploits in the wild have been reported.

Red Hat has released fixed versions of the rabbitmq-server4.3 RPM packages (version 4.3.4-0.1.hum1) for aarch64 and x86_64 architectures. Users should apply these updates promptly to remediate the vulnerability. No alternative mitigations or workarounds are documented. Patch status is confirmed by the vendor advisory.