CVE-2026-63335

Summary

RabbitMQ Java Client's inbound AMQP command assembly accepts a content header declaring a small body and then processes a larger body frame by throwing a raw UnsupportedOperationException from CommandAssembler. A broker peer that the client has connected to can use this malformed frame sequence to fail frame processing and tear down the client connection instead of receiving a clean protocol-level malformed-frame error.

This was discovered based on an existing vulnerability CVE-2017-15699.

Details

Inbound frames enter the client through SocketFrameHandler.readFrame, which returns frames parsed from the peer-controlled input stream (src/main/java/com/rabbitmq/client/impl/SocketFrameHandler.java:197). AMQConnection.MainLoop reads each frame (src/main/java/com/rabbitmq/client/impl/AMQConnection.java:692) and dispatches non-zero-channel frames to the channel while the connection is open (src/main/java/com/rabbitmq/client/impl/AMQConnection.java:748 and src/main/java/com/rabbitmq/client/impl/AMQConnection.java:766). The channel then passes the frame to the current command assembler through AMQChannel.handleFrame and AMQCommand.handleFrame (src/main/java/com/rabbitmq/client/impl/AMQChannel.java:121, src/main/java/com/rabbitmq/client/impl/AMQCommand.java:114). When a content-bearing method is followed by a content header, CommandAssembler.consumeHeaderFrame records the header's declared body size in remainingBodyBytes after only checking it against the configured maximum (src/main/java/com/rabbitmq/client/impl/CommandAssembler.java:126 through src/main/java/com/rabbitmq/client/impl/CommandAssembler.java:139). The body-frame path subtracts the received payload length from that remaining count before validating that the payload fits (src/main/java/com/rabbitmq/client/impl/CommandAssembler.java:145 through src/main/java/com/rabbitmq/client/impl/CommandAssembler.java:149), so a body frame larger than the declared size drives the count negative and reaches the raw UnsupportedOperationException at src/main/java/com/rabbitmq/client/impl/CommandAssembler.java:150 and src/main/java/com/rabbitmq/client/impl/CommandAssembler.java:151. AMQConnection catches the resulting throwable in frame processing and performs connection failure handling and final shutdown (src/main/java/com/rabbitmq/client/impl/AMQConnection.java:695 through src/main/java/com/rabbitmq/client/impl/AMQConnection.java:705).

PoC

poc.zip

bash ./poc/run.sh

Exception in thread "main" java.lang.UnsupportedOperationException: %%%%%% FIXME unimplemented

The UnsupportedOperationException: %%%%%% FIXME unimplemented fingerprint is the raw exception thrown at the negative remainingBodyBytes check in CommandAssembler.consumeBodyFrame. This line shows the malformed declared-size/body-size sequence reached the vulnerable assembler path.

Impact

The attacker model is a remote AMQP broker peer that the RabbitMQ Java Client application has accepted, including a malicious broker endpoint, a compromised broker, or routing that sends the client to an attacker-controlled peer. The peer needs a non-zero open channel that can receive a content-bearing server-to-client method such as basic.deliver, then sends the method frame, a content header declaring a body below the configured maximum, and a body frame whose payload exceeds that declared size. Under those conditions, the peer can force frame processing to fail with UnsupportedOperationException and close the AMQP connection, producing a client-side denial of service for work depending on that connection; the finding does not indicate memory corruption, data disclosure, or code execution.

The library allows Java code to interface to AMQP servers. Please see the specification page for more information on AMQP inter-operation and standards-conformance You will need an AMQP server, such as our very own RabbitMQ server, to use with the client library.

Security Fix(es):

The RabbitMQ Java client library allows Java and JVM-based applications to connect to and interact with RabbitMQ nodes. maxBodyLebgth was not used when receiving Message objects. Attackers could send a very large Message causing a memory overflow and triggering an OOM Error. Users of RabbitMQ may suffer from DoS attacks from RabbitMQ Java client which will ultimately exhaust the memory of the consumer. This vulnerability was patched in version 5.18.0.(CVE-2023-46120)

The RabbitMQ Java client library allows Java and JVM-based applications to connect to and interact with RabbitMQ nodes. Prior to 5.33.0, the AMQP connection tuning path records the negotiated AMQP frame_max value, but src/main/java/com/rabbitmq/client/impl/SocketFrameHandler.java and NettyFrameHandlerFactory continue to validate broker-controlled frame payload lengths against maxInboundMessageBodySize because the negotiated limit is not applied consistently through setMaxInboundFramePayloadSize. A malicious or compromised broker can send a method frame larger than the negotiated frame_max during or after connection establishment, causing the client to allocate and decode a protocol-invalid frame instead of rejecting it with MalformedFrameException. The protocol violation can disrupt the affected connection and cause client-side denial of service. This issue is fixed in version 5.33.0.(CVE-2026-61634)

The RabbitMQ Java client library allows Java and JVM-based applications to connect to and interact with RabbitMQ nodes. Prior to 5.31.0, inbound AMQP command assembly in src/main/java/com/rabbitmq/client/impl/CommandAssembler.java processes a content-bearing method and header whose remainingBodyBytes value is smaller than a following AMQP.FRAME_BODY payload. CommandAssembler.consumeBodyFrame subtracts the peer-controlled payload length before validating that it fits, drives remainingBodyBytes negative, and throws a raw UnsupportedOperationException instead of MalformedFrameException. A malicious or compromised broker peer can send this malformed sequence on an open nonzero channel to terminate frame processing and close the client connection, causing denial of service for work using that connection. This issue is fixed in version 5.31.0.(CVE-2026-63335)

The RabbitMQ Java client library allows Java and JVM-based applications to connect to and interact with RabbitMQ nodes. Prior to 5.33.0, com.rabbitmq.client.ConnectionFactory.useSslProtocol() and ConnectionFactory.useSslProtocol(String) configure com.rabbitmq.client.TrustEverythingTrustManager and leave hostname verification disabled, causing arbitrary server certificates, including self-signed certificates, to be accepted. A network attacker able to intercept a TLS connection can impersonate the RabbitMQ broker, read protected AMQP traffic, and modify traffic without certificate or hostname validation. The fix changes the production TLS helpers to use the JVM default trust store and enables hostname verification, while retaining an explicitly named development-only no-verification helper. This issue is fixed in version 5.33.0.(CVE-2026-63336)

The RabbitMQ Java client library allows Java and JVM-based applications to connect to and interact with RabbitMQ nodes. Prior to 5.33.1, src/main/java/com/rabbitmq/client/impl/ValueReader.java uses ValueReader.readBytes to accept a wire-declared contentLength below Integer.MAX_VALUE and allocate a byte array before checking the bytes available in the frame. A malicious AMQP peer can send a LongString or byte-array field with type tag S and a declared length such as 0x7FFFFFFE during the pre-authentication connection.start server-properties table, causing an approximately 2 GB allocation and…

Red Hat Lightwell has released com.rabbitmq:amqp-client 5.25.0.rhlw-00028 with backported fixes for CVE-2026-106121, CVE-2026-106122, CVE-2026-106123, CVE-2026-61634, CVE-2026-63335, CVE-2026-63336, CVE-2026-63337, CVE-2026-69219, and CVE-2026-69220.

CVE-2026-106121: RabbitMQ: JSONReader in the default JSON-RPC mapper never terminates on truncated input, causing DoS

CVE-2026-106122: RabbitMQ: Malformed UTF-8 in shortstr properties permanently disables RPC consumers

CVE-2026-106123: RabbitMQ Java client: plaintext broker credentials leaked in exception message from ConnectionFactoryConfigurator.load()

CVE-2026-61634: RabbitMQ Java client accepts broker frames larger than the negotiated AMQP frame_max

CVE-2026-63335: RabbitMQ Java client malformed body frame triggers raw command assembler exception

CVE-2026-63336: RabbitMQ Java client: TrustEverythingTrustManager used by default in useSslProtocol() enables MITM

CVE-2026-63337: RabbitMQ Java client: Unvalidated Class.forName in JSON-RPC ProcedureDescription enables arbitrary class loading

CVE-2026-69219: RabbitMQ Java client ValueReader: Oversized LongString/bytes length triggers OOM via unchecked allocation

CVE-2026-69220: RabbitMQ Java client ValueReader: Unbounded recursive table/array nesting causes StackOverflowError DoS

This patched artifact is a drop-in replacement for com.rabbitmq:amqp-client 5.25.0 from Maven Central.

Red Hat Lightwell has released com.rabbitmq:amqp-client 5.30.0.rhlw-00016 with backported fixes for CVE-2026-106121, CVE-2026-106122, CVE-2026-106123, CVE-2026-61634, CVE-2026-63335, CVE-2026-63336, CVE-2026-63337, CVE-2026-69219, and CVE-2026-69220.

CVE-2026-106121: RabbitMQ: JSONReader in the default JSON-RPC mapper never terminates on truncated input, causing DoS

CVE-2026-106122: RabbitMQ: Malformed UTF-8 in shortstr properties permanently disables RPC consumers

CVE-2026-106123: RabbitMQ Java client: plaintext broker credentials leaked in exception message from ConnectionFactoryConfigurator.load()

CVE-2026-61634: RabbitMQ Java client accepts broker frames larger than the negotiated AMQP frame_max

CVE-2026-63335: RabbitMQ Java client malformed body frame triggers raw command assembler exception

CVE-2026-63336: RabbitMQ Java client: TrustEverythingTrustManager used by default in useSslProtocol() enables MITM

CVE-2026-63337: RabbitMQ Java client: Unvalidated Class.forName in JSON-RPC ProcedureDescription enables arbitrary class loading

CVE-2026-69219: RabbitMQ Java client ValueReader: Oversized LongString/bytes length triggers OOM via unchecked allocation

CVE-2026-69220: RabbitMQ Java client ValueReader: Unbounded recursive table/array nesting causes StackOverflowError DoS

This patched artifact is a drop-in replacement for com.rabbitmq:amqp-client 5.30.0 from Maven Central.

The RabbitMQ Java client library allows Java and JVM-based applications to connect to and interact with RabbitMQ nodes. Prior to 5.31.0, inbound AMQP command assembly in src/main/java/com/rabbitmq/client/impl/CommandAssembler.java processes a content-bearing method and header whose remainingBodyBytes value is smaller than a following AMQP.FRAME_BODY payload. CommandAssembler.consumeBodyFrame subtracts the peer-controlled payload length before validating that it fits, drives remainingBodyBytes negative, and throws a raw UnsupportedOperationException instead of MalformedFrameException. A malicious or compromised broker peer can send this malformed sequence on an open nonzero channel to terminate frame processing and close the client connection, causing denial of service for work using that connection. This issue is fixed in version 5.31.0.

TuxCare rebuilt com.rabbitmq:amqp-client to address 4 CVEs. Fixed in 5.19.0-tuxcare.2.

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