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CVE-2026-67411

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

HIGH
7.1
CVSS Score
Published: September 25, 2026 at 04:26 PM UTC
Updated: October 8, 2026 at 04:46 PM UTC
2 products affected across 2 vendorsRabbitmq ServerRabbitmq Server

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Severity
HIGH7.1
Exploit prediction
EPSS 0.3%
SSVC
PoC

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Rabbitmq Server· Broadcom
95%
3.13.0 ≤ v < 3.13.184.0.0 ≤ v < 4.0.234.1.0 ≤ v < 4.1.144.2.0 ≤ v < 4.2.94.3.0 ≤ v < 4.3.3*
Affected range stops below 3.13.18, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.0.23, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.1.14, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.2.9, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.3.3, so it looks safe — our inference, not a vendor statement
Rabbitmq Server· Rabbitmq
90%
>= 3.13.0, < 3.13.18>= 4.0.0, < 4.0.23>= 4.1.0, < 4.1.14>= 4.2.0, < 4.2.9>= 4.3.0, < 4.3.3
Affected range stops below 3.13.18, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.0.23, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.1.14, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.2.9, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.3.3, so it looks safe — our inference, not a vendor statement

References (5)

x_refsource_CONFIRMExploitVendor Advisory
Source: cverecord
https://github.com/rabbitmq/rabbitmq-server/security/advisories/GHSA-4r6f-9cpw-f6g6
x_refsource_MISCPatch
Source: cverecord
https://github.com/rabbitmq/rabbitmq-server/commit/a7528314840c4f8dc9904684f9f97ffa7aac6349
x_refsource_MISCPatch
Source: cverecord
https://github.com/rabbitmq/rabbitmq-server/commit/edbead0eabbd65925d0dc914a22d6a29e155e646
x_refsource_MISCRelease Notes
Source: cverecord
https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.2.9
x_refsource_MISCRelease Notes
Source: cverecord
https://github.com/rabbitmq/rabbitmq-server/releases/tag/v4.3.3

SSVC — Action Prioritization

SSVCPoCNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.1HIGH[email protected]
Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-863

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