RabbitMQ failures to update the runtime user tags when an OAuth token is refreshed from one that previously granted the impersonator tag to one that no longer grants it. As a result, the connection retains stale #user.tags, causing the broker to still honor the impersonator privilege. The effect is that a session that once held elevated permissions can continue to publish messages on behalf of a foreign AMQP user after the token’s scopes have been downgraded. The flaw is an authorization bypass identified as CWE‑862.

RabbitMQ Server from the rabbitmq:rabbitmq-server product is vulnerable in all releases from 3.13.0 through 3.13.18, 4.0.0 to 4.0.23, 4.1.0 to 4.1.14, 4.2.0 to 4.2.9, and 4.3.0 to 4.3.4. The advisory confirms that versions 3.13.19, 4.0.24, 4.1.15, 4.2.10, and 4.3.5 and later contain the fix.

The CVSS score of 2.3 indicates low severity. The EPSS score is not available and the issue is not listed in CISA KEV. Exploitation requires an existing OAuth‑refreshable connection that had previously granted an impersonator tag, followed by a revocation of that tag. Because only the stale session state is affected and new connections are denied normally, the likelihood of successful exploitation is limited. Nonetheless, an adversary who can maintain or re‑establish such a session can continue to publish messages with elevated privileges.