Vulnerability-Lookup

GHSA-6G32-PXV4-2WFJ

Vulnerability from github – Published: 2026-08-18 16:32 – Updated: 2026-08-18 16:32

Summary

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

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.

Severity

7.5 (High)


                  
                    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

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{
  "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"
}

CVE-2026-63337 (GCVE-0-2026-63337)

Vulnerability from cvelistv5 – Published: 2026-08-18 16:27 – Updated: 2026-08-18 19:09

Title

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

Summary

The RabbitMQ Java client library allows Java and JVM-based applications to connect to and interact with RabbitMQ nodes. Prior to 5.33.0, com.rabbitmq.tools.jsonrpc.ProcedureDescription receives a javaReturnType value in an untrusted system.describe response and passes it through JSONUtil.tryFill, setJavaReturnType, and computeReturnTypeAsJavaClass to Class.forName(javaReturnType) with initialization enabled. An attacker able to answer the JsonRpcClient request through a shared broker or network interception can select a class already present in the victim JVM and trigger its static initializer, while JsonRpcClient.java later passes getReturnType output to mapper.parse and may also create type confusion. Successful exploitation can affect confidentiality, integrity, and availability in the client process. This issue is fixed in version 5.33.0.

Severity

7.5 (High)


                        
                          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

SSVC

Exploitation: poc Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-18 19:08 UTC

CWE

CWE-470 - Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection')

Assigner

GitHub_M mitre root

References

6 references

URL	Tags
https://github.com/rabbitmq/rabbitmq-java-client/…	x_refsource_CONFIRM
https://github.com/rabbitmq/rabbitmq-java-client/…	x_refsource_MISC
https://github.com/rabbitmq/rabbitmq-java-client/…	x_refsource_MISC
https://github.com/rabbitmq/rabbitmq-java-client/…	x_refsource_MISC
https://github.com/rabbitmq/rabbitmq-java-client/…	x_refsource_MISC
https://github.com/rabbitmq/rabbitmq-java-client/…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
rabbitmq	rabbitmq-java-client	Affected: < 5.33.0

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
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                "id": "CVE-2026-63337",
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                  },
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                    "Technical Impact": "total"
                  }
                ],
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                "timestamp": "2026-08-18T19:08:47.576010Z",
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          "value": "The RabbitMQ Java client library allows Java and JVM-based applications to connect to and interact with RabbitMQ nodes. Prior to 5.33.0, com.rabbitmq.tools.jsonrpc.ProcedureDescription receives a javaReturnType value in an untrusted system.describe response and passes it through JSONUtil.tryFill, setJavaReturnType, and computeReturnTypeAsJavaClass to Class.forName(javaReturnType) with initialization enabled. An attacker able to answer the JsonRpcClient request through a shared broker or network interception can select a class already present in the victim JVM and trigger its static initializer, while JsonRpcClient.java later passes getReturnType output to mapper.parse and may also create type confusion. Successful exploitation can affect confidentiality, integrity, and availability in the client process. This issue is fixed in version 5.33.0."
        }
      ],
      "metrics": [
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          "cvssV4_0": {
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  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

GHSA-6G32-PXV4-2WFJ

CVE-2026-63337 (GCVE-0-2026-63337)

Tags

Sightings

Nomenclature