high

CVE-2026-63337

Maven · com.rabbitmq:amqp-client

Summary

RabbitMQ Java client: Unvalidated Class.forName in JSON-RPC ProcedureDescription enables arbitrary class loading

Severity
high
EPSS
0.6% (p46)
CWE
CWE-470
Also known as
GHSA-6g32-pxv4-2wfj
Published
2026-08-18
Updated
2026-08-18

Advisory details

The JSON-RPC tools in com.rabbitmq.tools.jsonrpc perform Class.forName(javaReturnType) with initialize=true on class names received from untrusted AMQP messages, without any validation or allowlist.

Vulnerable code (ProcedureDescription.java:101-127): When a JsonRpcClient connects, it calls system.describe and receives a service description from the AMQP queue. The response JSON includes javaReturnType fields that are reflectively set via JSONUtil.tryFill(), triggering setJavaReturnType() → computeReturnTypeAsJavaClass() → Class.forName(javaReturnType).

Attack scenario:

  1. Victim uses JsonRpcClient to connect to a JSON-RPC service via RabbitMQ
  2. Attacker (co-tenant on shared broker, or MITM) intercepts the system.describe request
  3. Attacker responds with crafted javaReturnType values
  4. Victim's client calls Class.forName(attackerInput) with default initialize=true
  5. Static initializers of attacker-specified classes execute in victim's JVM

Additionally, the loaded class from getReturnType() is passed to mapper.parse(replyStr, expectedType) at JsonRpcClient.java:168, potentially enabling type-confusion.

Recommended fix: Use Class.forName(javaReturnType, false, classLoader) to prevent static initializer execution, or add an allowlist of permitted return types.

CWE: CWE-470

Reply from reporter (2026-06-29): Thanks for the quick turnaround. Fix looks good. Looking forward to the CVE assignment.

References

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Sources: CISA KEV (public domain), OSV.dev & GitHub Advisory Database (CC-BY-4.0), FIRST EPSS, NVD/CWE (public domain). Served live from the Stateward advisory database.