RabbitMQ Java client ValueReader: Unbounded recursive table/array nesting causes StackOverflowError DoS

Summary

ValueReader.readTable() and readArray() recursively call readFieldValue() with no depth limit. A malicious AMQP peer can crash the client JVM by sending a deeply nested table structure.

Vulnerable Code

src/main/java/com/rabbitmq/client/impl/ValueReader.java lines 139-155 and 237-249:

private static Map<String, Object> readTable(DataInputStream in) throws IOException {
    long tableLength = unsignedExtend(in.readInt());
    // ...
    while(tableIn.available() > 0) {
        String name = readShortstr(tableIn);
        Object value = readFieldValue(tableIn);  // recursive call
    }
}

static Object readFieldValue(DataInputStream in) throws IOException {
    switch(in.readUnsignedByte()) {
      case 'F': value = readTable(in);  // mutual recursion
      case 'A': value = readArray(in);  // mutual recursion
    }
}

Attack Scenario

A malicious AMQP server (or MitM) sends a connection.start frame with ~580 levels of nested tables. Each level costs ~7 bytes (4-byte length + 1-byte key length + 1-byte key + 1-byte type tag), totaling ~4060 bytes within the 131,072 byte max frame size. With the default JVM stack (~512KB, ~864 bytes/frame), this triggers StackOverflowError, killing the I/O thread.

Exploitable pre-authentication since connection.start is the very first server frame.

Impact

Denial of service. StackOverflowError kills the client I/O thread.

CWE

CWE-674: Uncontrolled Recursion

Remediation

Add a depth counter to readTable/readArray/readFieldValue and throw MalformedFrameException when exceeding a threshold (e.g., 32).