A reflected cross‑site scripting flaw exists in RabbitMQ’s OAuth bootstrap JavaScript endpoint. The endpoint injects a bearer token from the Authorization header or an access_token cookie directly into the JavaScript payload without proper escaping. When the JavaScript is delivered to the RabbitMQ management UI, the unescaped token content is executed in the context of the management UI origin, allowing an attacker to run arbitrary code as the victim in the browser.

RabbitMQ Server versions 4.2.0 through 4.2.7 and 4.3.0 through 4.3.1, and related releases that enable the management plugin with management.oauth_enabled set to true, are affected. The issue is fixed in versions 4.2.8 and 4.3.2.

The CVSS score of 7.5 assigns this vulnerability a high severity rating. The endpoint is reachable without authentication when management.oauth_enabled is true, so an attacker can trigger the flawed endpoint with a crafted Authorization header or by planting an access_token cookie on the management host. Successful exploitation, however, requires a victim to load the JavaScript delivered by the endpoint in a browser; the attacker cannot directly inject code into the victim’s browsing context without the victim interacting with the management UI. The EPSS is not available and the issue is not listed in the CISA KEV catalog, suggesting no evidence of widespread exploitation at this time.