The RabbitMQ stream listener misuse of the configured frame-size limit during authentication causes memory exhaustion in rabbit_stream_core. The vulnerability is a classic No Resource Exhaustion flaw (CWE-770). A remote unauthenticated client can transmit oversized frame lengths before the broker applies the limit, causing the broker's memory buffers to grow uncontrollably and potentially crash or become unresponsive. This results in a denial‑of‑service condition that can affect the availability of all services relying on the broker.

The flaw exists in RabbitMQ Server versions earlier than 4.2.6 from the vendor rabbitmq. Any deployment that has not applied the 4.2.6 release or a later patch is susceptible. The affected component is the stream listener that performs frame assembly during authentication and before Tune negotiation. All brokers exposing the stream protocol over the network are at risk.

The CVSS score of 7.5 indicates a high severity, and the issue is not listed the CISA Known Exploited Vulnerabilities catalog. The EPSS score of < 1% indicates a very low, but non‑zero, exploitation probability, but the description states that an unauthenticated remote client can trigger the flaw by sending specially crafted messages to the broker's stream listener. Once enacted, the broker will allocate memory in rabbit_stream_core until resources are exhausted, leading to a service disruption. Applying the 4.2.6 fix restores enforcement of the frame‑size limit and eliminates the DoS vector.