# CVE-2026-67232: RabbitMQ: Web-MQTT decompression bomb

CVE-2026-67232 is fixed in rabbitmq-server on 1 platform, first by rabbitmq-server 4.0.5-10ubuntu5.2, released September 25, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-67232
- Priority: High
- CVSS: 7.5 (Important)
- EPSS: 0.0039
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 23, 2026
- Weakness: Improper Handling of Highly Compressed Data (Data Amplification)
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-67232

## Description

RabbitMQ is a messaging and streaming broker. Prior to versions 3.13.15, 4.0.20, 4.1.11, 4.2.6, and 4.3.0, The cowboy WebSocket options at line 117 set compress => true, enabling RFC 7692 permessage-deflate negotiation. The handler does not set max_frame_size, so cowboy's default of infinity applies. cowlib's cow_ws:parse_payload/9 calls zlib:inflate/2 on the compressed payload with no output-size limit. An attacker can negotiate permessage-deflate during the WebSocket upgrade and send a frame containing a zlib bomb (e.g. 50 KB → 5 GB). Decompression occurs in the connection process before websocket_handle/2 ever sees the MQTT bytes. An unauthenticated attacker can crash a RabbitMQ node running the Web-MQTT plugin by sending a single highly-compressed WebSocket frame (a few KB on the wire) that inflates to gigabytes in memory. The cowboy WebSocket handler decompresses the entire frame before the MQTT CONNECT packet is processed, so no credentials are required. Preconditions include rabbitmq_web_mqtt plugin enabled (not default, but common for browser clients) Network reachability to port 15675/15676 No authentication required. This issue is fixed in versions 3.13.15, 4.0.20, 4.1.11, 4.2.6, and 4.3.0.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | rabbitmq-server Debian 14 | 4.3.0-2 | [DEBIAN-CVE-2026-67232](https://patchblox.com/security/data/fix/linux/debian-cve-2026-67232.md) | Sep 25, 2026 |
| Linux | rabbitmq-server Ubuntu 18.04.6 LTS (bionic) | 3.6.10-1ubuntu0.5+esm1 | [rabbitmq-server 3.6.10-1ubuntu0.5+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-rabbitmq-server-3.6.10-1ubuntu0.5-esm1.md) | Oct 19, 2026 |
| Linux | rabbitmq-server Ubuntu 20.04 LTS (focal) | 3.8.3-0ubuntu0.3+esm2 | [rabbitmq-server 3.8.3-0ubuntu0.3+esm2](https://patchblox.com/security/data/fix/linux/ubuntu-focal-rabbitmq-server-3.8.3-0ubuntu0.3-esm2.md) | Oct 19, 2026 |
| Linux | rabbitmq-server Ubuntu 22.04.1 LTS (jammy) | 3.9.27-0ubuntu0.6 | [rabbitmq-server 3.9.27-0ubuntu0.6](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-rabbitmq-server-3.9.27-0ubuntu0.6.md) | Oct 19, 2026 |
| Linux | rabbitmq-server Ubuntu 24.04.5 LTS (noble) | 3.12.1-1ubuntu1.7 | [rabbitmq-server 3.12.1-1ubuntu1.7](https://patchblox.com/security/data/fix/linux/ubuntu-noble-rabbitmq-server-3.12.1-1ubuntu1.7.md) | Oct 19, 2026 |
| Linux | rabbitmq-server Ubuntu 26.04.1 LTS (resolute) | 4.0.5-10ubuntu5.2 | [rabbitmq-server 4.0.5-10ubuntu5.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-rabbitmq-server-4.0.5-10ubuntu5.2.md) | Sep 25, 2026 |

---

Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data

Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.