GHSA-6G32-PXV4-2WFJ
Vulnerability from github – Published: 2026-08-18 16:32 – Updated: 2026-08-18 16:32The 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.
{
"affected": [
{
"package": {
"ecosystem": "Maven",
"name": "com.rabbitmq:amqp-client"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "5.33.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-63337"
],
"database_specific": {
"cwe_ids": [
"CWE-470"
],
"github_reviewed": true,
"github_reviewed_at": "2026-08-18T16:32:29Z",
"nvd_published_at": null,
"severity": "HIGH"
},
"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.\n\n**Vulnerable code** (`ProcedureDescription.java:101-127`):\nWhen 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()` \u2192 `computeReturnTypeAsJavaClass()` \u2192 `Class.forName(javaReturnType)`.\n\n**Attack scenario:**\n1. Victim uses `JsonRpcClient` to connect to a JSON-RPC service via RabbitMQ\n2. Attacker (co-tenant on shared broker, or MITM) intercepts the `system.describe` request\n3. Attacker responds with crafted `javaReturnType` values\n4. Victim\u0027s client calls `Class.forName(attackerInput)` with default `initialize=true`\n5. Static initializers of attacker-specified classes execute in victim\u0027s JVM\n\nAdditionally, the loaded class from `getReturnType()` is passed to `mapper.parse(replyStr, expectedType)` at `JsonRpcClient.java:168`, potentially enabling type-confusion.\n\n**Recommended fix:** Use `Class.forName(javaReturnType, false, classLoader)` to prevent static initializer execution, or add an allowlist of permitted return types.\n\n**CWE:** CWE-470\n\n---\n\n**Reply from reporter (2026-06-29):** Thanks for the quick turnaround. Fix looks good. Looking forward to the CVE assignment.",
"id": "GHSA-6g32-pxv4-2wfj",
"modified": "2026-08-18T16:32:29Z",
"published": "2026-08-18T16:32:29Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/rabbitmq/rabbitmq-java-client/security/advisories/GHSA-6g32-pxv4-2wfj"
},
{
"type": "WEB",
"url": "https://github.com/rabbitmq/rabbitmq-java-client/pull/2000"
},
{
"type": "WEB",
"url": "https://github.com/rabbitmq/rabbitmq-java-client/pull/2002"
},
{
"type": "WEB",
"url": "https://github.com/rabbitmq/rabbitmq-java-client/commit/0032f75f9dc3df847f94b2b85a16119250bf63cb"
},
{
"type": "WEB",
"url": "https://github.com/rabbitmq/rabbitmq-java-client/commit/9f8e7efd0c648f235dc0e96232ae7efa75ea4fa8"
},
{
"type": "PACKAGE",
"url": "https://github.com/rabbitmq/rabbitmq-java-client"
},
{
"type": "WEB",
"url": "https://github.com/rabbitmq/rabbitmq-java-client/releases/tag/v5.33.0"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "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",
"type": "CVSS_V4"
}
],
"summary": "RabbitMQ Java client: Unvalidated Class.forName in JSON-RPC ProcedureDescription enables arbitrary class loading"
}
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