RabbitMQ Java client: Unvalidated Class.forName in JSON-RPC ProcedureDescription enables arbitrary class loading
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:
- Victim uses
JsonRpcClientto connect to a JSON-RPC service via RabbitMQ - Attacker (co-tenant on shared broker, or MITM) intercepts the
system.describerequest - Attacker responds with crafted
javaReturnTypevalues - Victim's client calls
Class.forName(attackerInput)with defaultinitialize=true - 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.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Java / Kotlin (Maven) | com.rabbitmq:amqp-client | < 5.33.0 | 5.33.0 |
References
- https://github.com/rabbitmq/rabbitmq-java-client/security/advisories/GHSA-6g32-pxv4-2wfj
- https://github.com/rabbitmq/rabbitmq-java-client/pull/2000
- https://github.com/rabbitmq/rabbitmq-java-client/pull/2002
- https://github.com/rabbitmq/rabbitmq-java-client/commit/0032f75f9dc3df847f94b2b85a16119250bf63cb
- https://github.com/rabbitmq/rabbitmq-java-client/commit/9f8e7efd0c648f235dc0e96232ae7efa75ea4fa8
- https://github.com/rabbitmq/rabbitmq-java-client
- https://github.com/rabbitmq/rabbitmq-java-client/releases/tag/v5.33.0
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L- Weakness (CWE)
CWE-470- Platform
- Java / Kotlin (Maven)
- Package
com.rabbitmq:amqp-client- Disclosed
- 18.08.2026
- Updated
- 11.10.2026 13:20
Sources and licenses
OSV / GitHub Advisory Database - GHSA-6g32-pxv4-2wfj - CC BY 4.0
Vulnerability history: com.rabbitmq:amqp-client
All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 12
- First → latest
- 10.2018 10.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 4
- Medium 7
- Low 1
Disclosures per year
- 2018: 1
- 2019: 0
- 2020: 0
- 2021: 0
- 2022: 0
- 2023: 1
- 2024: 0
- 2025: 0
- 2026: 10
-
RabbitMQ Java client: Unvalidated Class.forName in JSON-RPC ProcedureDescription enables arbitrary class loading this entry
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