Unsafe reflection in RabbitMQ Java Client Library - CVE-2026-63337
Published: July 9, 2026 / Updated: August 19, 2026
Vulnerability identifier: #VU137271
CSH Severity: High
CVSS v4: 8.8 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-63337
CWE-ID: CWE-470
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to use of externally-controlled input to select classes or code in ProcedureDescription in com.rabbitmq.tools.jsonrpc when processing a crafted JSON-RPC service description from untrusted AMQP messages. A remote attacker can send a crafted system.describe response with attacker-controlled javaReturnType values to execute arbitrary code.
The issue is triggered when a JsonRpcClient connects to a JSON-RPC service, and the selected class may also be used as the expected type for reply parsing.
Affected software
RabbitMQ Java Client Library
How to mitigate CVE-2026-63337
Install security update from vendor's website.
RabbitMQ Java Client Library - update to 5.33.0