# CVE-2026-67232: RabbitMQ zlib bomb denial of service in Web-MQTT WebSocket

Source: https://junglewise.ai/threats/cve-2026-67232-rabbitmq-is-a-messaging-and-streaming-broker-prior-to-versions-3  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-23. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-67232 · Severity: info · Published 2026-09-23

RabbitMQ is a messaging broker used to route messages between applications. The Web-MQTT plugin enables browser clients to connect via WebSocket, but prior to the fixed versions, it did not limit decompressed frame sizes. An unauthenticated attacker can send a highly compressed WebSocket frame (a few kilobytes on the wire) that decompresses to gigabytes, crashing the RabbitMQ node without needing to log in or send any valid credentials.

Technologies: [RabbitMQ](https://junglewise.ai/threats/technologies/rabbitmq-rabbitmq). Vendors: [RabbitMQ](https://junglewise.ai/threats/vendors/rabbitmq).

## Quick answers

**Is CVE-2026-67232 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-67232 being exploited in the wild.

**How severe is CVE-2026-67232?** Informational severity, published 23 September 2026.

**Which products and versions are affected?** RabbitMQ before 3.13.15, 4.0.20, 4.1.11, 4.2.6, and 4.3.0.

**Is there a fix for CVE-2026-67232?** A patch was published on 2026-04-23: Patches released for versions 3.13.15, 4.0.20, 4.1.11, 4.2.6, and 4.3.0 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-67232 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-67232?** Check whether you run RabbitMQ at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a zlib bomb denial of service in RabbitMQ's Web-MQTT WebSocket handler. The cowboy WebSocket configuration enables RFC 7692 permessage-deflate compression but does not set max_frame_size, allowing cowlib's cow_ws:parse_payload/9 to decompress frames to unlimited size. An unauthenticated attacker with network access to the WebSocket port can send a single compressed frame that inflates to gigabytes in memory before the MQTT CONNECT packet is ever processed, crashing the connection process. The fix adds a default max_frame_size limit that is enforced before authentication.

## Affected products

- RabbitMQ RabbitMQ before 3.13.15, 4.0.20, 4.1.11, 4.2.6, and 4.3.0

## Timeline

- 2026-09-23: disclosed
- 2026-04-23: patched: Patches released for versions 3.13.15, 4.0.20, 4.1.11, 4.2.6, and 4.3.0

## References

- [https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.2.6](https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.2.6)
- [https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.3.0](https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.3.0)

## Related threats

- [RabbitMQ OAuth privilege escalation via stale token tags](https://junglewise.ai/threats/cve-2026-67420-rabbitmq-is-a-messaging-and-streaming-broker-from-3-13-0-until-3)
- [RabbitMQ topic exchange denial of service via duplicate matchers](https://junglewise.ai/threats/cve-2026-67419-rabbitmq-is-a-messaging-and-streaming-broker-prior-to-4-3-5-an)
- [RabbitMQ Shovel denial of service via atom exhaustion](https://junglewise.ai/threats/cve-2026-67415-rabbitmq-is-a-messaging-and-streaming-broker-from-4-2-0-until-4-2)
- [RabbitMQ MQTT loopback user bypass via PROXY Protocol](https://junglewise.ai/threats/cve-2026-67411-rabbitmq-is-a-messaging-and-streaming-broker-from-3-13-0-until-3)
- [RabbitMQ OAuth2 client secret exposure via unauthenticated endpoint](https://junglewise.ai/threats/cve-2026-67410-rabbitmq-is-a-messaging-and-streaming-broker-from-4-2-0-until-4-3)