CVE-2026-75516: RabbitMQ Java client: Frame-level OOM: Math.min(maxInboundMessageBodySize, 0) defeats frame size enforcement
The RabbitMQ Java client library allows Java and JVM-based applications to connect to and interact with RabbitMQ nodes. Prior to 5.34.0, AMQConnection.start() applies Math.min(maxInboundMessageBodySize, frameMax) after Connection.Tune negotiation even though AMQP defines frameMax value zero as unlimited and ConnectionFactory.DEFAULTFRAMEMAX is zero. When the client default and server-negotiated value are both zero, the result is passed to Utils.framePayloadLimit(int), which interprets zero as Integer.MAXVALUE and disables the configured maxInboundMessageBodySize cap. A malicious AMQP server, or a man-in-the-middle attacker able to modify Connection.Tune and inject frames into the connection, can then send an oversized frame of any frame type, causing Frame.readFrom() to allocate a large byte array before content-level validation and potentially terminate the client process through memory exhaustion. This issue is fixed in version 5.34.0.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
RabbitMQ Java clientto a version that resolves this vulnerability.Fixed in 5.34.0
Event History
Frequently Asked Questions
Which deployments are exposed to this issue?
Java and other JVM-based applications using RabbitMQ Java client versions before 5.34.0 are affected when the effective negotiated frameMax is zero. This includes the default client frame-max setting, because ConnectionFactory.DEFAULT_FRAME_MAX is zero.
What must an attacker be able to do?
An attacker must control a malicious AMQP server, or be able to act as a man-in-the-middle who modifies Connection.Tune and injects frames into the connection. They can then send an oversized AMQP frame and trigger large memory allocation in the client.
What happens if exploitation succeeds?
The client can allocate a large byte array while reading the frame, before content-level validation occurs. This can exhaust memory and terminate the client process.
What is the remediation?
Upgrade the RabbitMQ Java client to version 5.34.0, which fixes the frame-size enforcement issue.