RabbitMQ: Web MQTT with PROXY Protocol enabled: a loopback-only user permission bypass (CVE-2026-67411) | HOL Guard CVE

Medium · CVSS 6.0CVE-2026-67411

RabbitMQ: Web MQTT with PROXY Protocol enabled: a loopback-only user permission bypass

Answer in brief

CVE-2026-67411 records a Medium severity (CVSS 6.0) vulnerability in RabbitMQ: Web MQTT with PROXY Protocol enabled: a loopback-only user permission bypass. The current sources do not mark it as known exploited. The current feed maps rabbitmq/rabbitmq-server (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 25, 2026Updated Sep 25, 2026Source checked Sep 25, 2026First seen by HOL Sep 25, 2026Material review Sep 25, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 6.0
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 6.0. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps rabbitmq/rabbitmq-server (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
rabbitmq/rabbitmq-servergeneric	>=4.3.0 <4.3.3 \|\| >=4.2.0 <4.2.9 \|\| >=4.1.0 <4.1.14 \|\| >=4.0.0 <4.0.23 \|\| >=3.13.0 <3.13.18	4.3.3, 4.2.9, 4.1.14, 4.0.23, 3.13.18

Recommended response

Check inventory. Check lockfiles and deployed manifests for rabbitmq/rabbitmq-server.
Review the reported fix. Update rabbitmq/rabbitmq-server to 4.3.3 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 25, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 25, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 25, 2026

Sources and claim methodology

Upstream source description

RabbitMQ is a messaging and streaming broker. From 3.13.0 until 3.13.18, 4.0.23, 4.1.14, 4.2.9, and 4.3.3, native MQTT and MQTT over WebSocket behind a trusted PROXY Protocol frontend could lose the proxy-derived client address before the MQTT authentication path checked loopback_users, causing the frontend-to-broker address to be treated as loopback. An attacker who can reach the trusted frontend and has valid credentials for a loopback-restricted account can therefore bypass the source-address restriction; the issue does not bypass password authentication. This issue is fixed in versions 3.13.18, 4.0.23, 4.1.14, 4.2.9, and 4.3.3.

Quoted source text, attributed separately from HOL analysis.