CVE-2026-63337Network attack vector

Static-initializer execution via untrusted Class.forName

Published Aug 18, 2026 · Updated Aug 18, 2026

Unsafe reflection in RabbitMQ Java Client before 5.33.0 allows attackers to execute static initializers via crafted system.describe responses. ProcedureDescription reflects the untrusted javaReturnType field from a system.describe reply through JSONUtil.tryFill into setJavaReturnType, which calls Class.forName(javaReturnType) with initialization enabled and no validation or allowlist. Reachability requires control of the JSON-RPC service response, such as through a shared broker or network interception; the loaded class is later reused as a parse target, adding type-confusion risk in the client JVM.

CVSS severity7.5
High
EPSS probability0.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Unsafe reflection in RabbitMQ Java Client before 5.33.0 allows attackers to execute static initializers via crafted system.describe responses. ProcedureDescription reflects the untrusted javaReturnType field from a system.describe reply through JSONUtil.tryFill into setJavaReturnType, which calls Class.forName(javaReturnType) with initialization enabled and no validation or allowlist. Reachability requires control of the JSON-RPC service response, such as through a shared broker or network interception; the loaded class is later reused as a parse target, adding type-confusion risk in the client JVM.

The record

CVE
CVE-2026-63337
Published
Aug 18, 2026
Updated
Aug 18, 2026
Vendor
RabbitMQ
Product
RabbitMQ Java Client
Classifications
CWE-470
Attack vector
network
Privileges
Unavailable

Timeline

How it unfolded

  1. Aug 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 5.33.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesUnavailable in this record.

What is affected?

RabbitMQ · RabbitMQ Java Clientversion=< 5.33.0

Published CVSS scores

7.5GitHub, Inc.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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

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

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo