CVE-2026-63335: Amqp client RabbitMQ Java Client Malformed Body Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-qx7j-jv8m-fppr",
  "modified" : "2026-08-18T16:32:43Z",
  "published" : "2026-08-18T16:32:42Z",
  "aliases" : [ "CVE-2026-63335" ],
  "summary" : "RabbitMQ Java client malformed body frame triggers raw command assembler exception",
  "details" : "### Summary\nRabbitMQ 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. \n\nThis was discovered based on an existing vulnerability CVE-2017-15699.\n\n### Details\nInbound 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`).\n\n### PoC\n[poc.zip](https://github.com/user-attachments/files/28182717/poc.zip)\n\n```bash\nbash ./poc/run.sh\n```\n\n```text\nException in thread \"main\" java.lang.UnsupportedOperationException: %%%%%% FIXME unimplemented\n```\n\nThe `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.\n\n### Impact\nThe 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.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:N/SI:N/SA:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "com.rabbitmq:amqp-client"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.31.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 5.30.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/rabbitmq/rabbitmq-java-client/security/advisories/GHSA-qx7j-jv8m-fppr"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rabbitmq/rabbitmq-java-client/pull/1959"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rabbitmq/rabbitmq-java-client/pull/1960"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rabbitmq/rabbitmq-java-client/commit/31735344d9f9dfc53740b67f06e560e8846b9322"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rabbitmq/rabbitmq-java-client/commit/abd6d60d4e2bfc1a327dc90ab246b2e8aca1f33b"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/rabbitmq/rabbitmq-java-client"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rabbitmq/rabbitmq-java-client/releases/tag/v5.31.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-18T16:32:42Z",
    "nvd_published_at" : null
  }
}