CVE-2026-77406: RabbitMQ amqp091-go: Consumer Message Flooding via Signed-to-Unsigned Integer Casting in Qos Configuration

A logic and resource exhaustion vulnerability exists in the AMQP client’s Quality of Service (Qos) configuration method. The Qos function accepts signed integers (int) for the prefetchCount and prefetchSize parameters but casts them directly to unsigned integers (uint16 and uint32, respectively) when formatting the wire-level frame.

If a developer passes a negative integer (such as -1) to these parameters—frequently intended as a sentinel value meaning “no change” or “no limit”—the application performs an implicit signed-to-unsigned conversion. This wraps the values to their absolute maximum limit ($65535$ and $4294967295$). Consequently, a consumer expecting restricted message delivery rates is suddenly flooded with an unlimited volume of messages, potentially exhausting memory resources and crashing the application.