CVE-2026-44839: RabbitMQ Messaging Broker Vulnerability

CVE-2026-44839 Overview

CVE-2026-44839 affects RabbitMQ, an open-source messaging and streaming broker used widely across enterprise environments. The vulnerability is classified under [CWE-80] (Improper Neutralization of Script-Related HTML Tags in a Web Page). It impacts RabbitMQ releases from version 3.7.0 up to but not including 4.1.2 and 4.0.13. Maintainers fixed the issue in versions 4.1.2 and 4.0.13.

Critical Impact

An authenticated attacker with high privileges can inject script content that executes in the browser of another RabbitMQ management user, leading to confidentiality impact on the targeted session.

Affected Products

• RabbitMQ Server versions 3.7.0 through 4.1.1
• RabbitMQ Server 4.0.x prior to 4.0.13
• RabbitMQ Server 4.1.x prior to 4.1.2

Discovery Timeline

• 2026-05-27 - CVE-2026-44839 published to NVD
• 2026-05-27 - Last updated in NVD database

Technical Details for CVE-2026-44839

Vulnerability Analysis

The vulnerability is a stored Cross-Site Scripting (XSS) issue in RabbitMQ, mapped to [CWE-80]. RabbitMQ exposes a web-based management interface that renders user-supplied values such as queue names, exchange definitions, virtual host metadata, and policy descriptions. When the management UI fails to neutralize HTML and script tags in these fields, attacker-controlled markup is stored server-side and rendered to other operators visiting the same view.

The attack requires high privileges and user interaction. An authenticated administrator or operator must create or modify an object containing the malicious payload, and a second user must subsequently load the affected page. The scope remains within the management UI, and the issue does not directly impact integrity or availability of broker operations.

The RabbitMQ team addressed the flaw in commit 7f54319279d1ece161ae0b4cdc6f0e58a4045eb5. See the GitHub Security Advisory for the official disclosure.

Root Cause

The root cause is improper neutralization of script-related HTML tags before storing or rendering user-supplied content in the RabbitMQ management interface. Output encoding routines did not consistently escape tag delimiters, allowing markup to survive into the rendered DOM.

Attack Vector

The attack vector is Network with high attack complexity. The attacker authenticates to RabbitMQ with elevated privileges, submits a crafted payload through a management API endpoint or UI form, then waits for a victim operator to view the resource. The injected script executes in the victim's browser session against the management origin. Refer to the GitHub Commit Changes for the precise sanitization logic introduced.

Detection Methods for CVE-2026-44839

Indicators of Compromise

• RabbitMQ object names, tags, or descriptions containing <script>, onerror=, onload=, or other HTML event handler syntax
• Unexpected outbound requests from operator browsers to attacker-controlled domains while viewing the RabbitMQ management UI
• Unusual administrative API calls originating from operator sessions immediately after viewing management pages

Detection Strategies

• Audit RabbitMQ definitions exports (rabbitmqctl export_definitions) for HTML tags or JavaScript syntax embedded in queue, exchange, vhost, user, or policy names and metadata
• Inspect reverse proxy and management plugin access logs for PUT and POST requests containing encoded <, >, or script substrings against /api/queues, /api/exchanges, /api/vhosts, and /api/policies
• Monitor browser content security policy (CSP) violation reports if CSP is enabled in front of the management UI

Monitoring Recommendations

• Forward RabbitMQ management HTTP access logs and audit logs to a centralized log platform for correlation against operator browsing activity
• Alert on creation or modification of management objects whose names or descriptions exceed expected character sets
• Track use of high-privilege RabbitMQ accounts (administrator tag) and review changes they make to object metadata

How to Mitigate CVE-2026-44839

Immediate Actions Required

• Upgrade RabbitMQ to version 4.1.2 or 4.0.13 or later as published by the maintainers
• Review existing queues, exchanges, vhosts, users, and policies for embedded HTML or script content and remove or rename affected objects
• Rotate management UI session cookies and revoke API tokens for accounts that may have viewed malicious payloads

Patch Information

The fix is contained in RabbitMQ commit 7f54319279d1ece161ae0b4cdc6f0e58a4045eb5 and shipped in releases 4.1.2 and 4.0.13. Review the GitHub Security Advisory GHSA-fh5r-jpm3-fjwp for the canonical patch reference.

Workarounds

• Restrict access to the RabbitMQ management UI to trusted networks using firewall rules or a reverse proxy with IP allowlisting
• Limit accounts with the administrator and management tags to the minimum required and avoid sharing high-privilege credentials
• Deploy a strict Content Security Policy at the reverse proxy layer to constrain inline script execution in the management UI

# Configuration example: upgrade and verify RabbitMQ version
sudo systemctl stop rabbitmq-server
sudo apt-get update && sudo apt-get install --only-upgrade rabbitmq-server
sudo systemctl start rabbitmq-server
rabbitmqctl version
# Expected output: 4.1.2 or 4.0.13 or later