CVE-2026-79921: amqp091-go has a Potential Memory Exhaustion/Protocol Violation via Broker-Controlled Oversized Payload

Summary A vulnerability exists in the amqp091-go client library where a compromised or malicious AMQP broker can force the client to allocate resources for and process content body frames that exceed the negotiated framemax limit. This can lead to unexpected memory consumption or application-layer denial of service (DoS), bypassing the protocol's built-in framing constraints.

Details During a standard AMQP 0-9-1 connection handshake, the client and the broker negotiate a maximum frame size (framemax), for example, 4096 bytes.

However, after negotiation, a malicious broker can send a valid basic.deliver sequence containing a content body frame whose header declares a payload size larger than the negotiated framemax. Instead of enforcing the agreed-upon limit and closing the connection with a frame-error (as mandated by the AMQP 0-9-1 specification), the amqp091-go client:

1. Accepts the broker-declared oversized frame size. 2. Allocates memory based on this oversized declaration. 3. Reads the payload, assembles it into the message, and delivers it to the consumer.

Impact

- Denial of Service (DoS): If a broker sends extremely large frame sizes, it can trigger significant memory allocations on the client side, potentially leading to Out-Of-Memory (OOM) crashes. - Protocol Violation: The client fails to enforce negotiated connection parameters, trusting the broker implicitly even after constraints have been established.