Affected: rucio

Rucio is a software framework that provides functionality to organize, manage, and access large volumes of scientific data using customizable policies. A reflected Cross-site Scripting vulnerability was located in versions prior to 35.8.3, 38.5.4, and 39.3.1 in the rendering of the ExceptionMessage of the WebUI 500 error which could allow attackers to steal login session tokens of users who navigate to a specially crafted URL. Versions 35.8.3, 38.5.4, and 39.3.1 fix the issue.

Affected: PyPI: rucio-webui

### Summary A reflected Cross-site Scripting vulnerability was located in the rendering of the ExceptionMessage of the WebUI 500 error which could allow attackers to steal login session tokens of users who navigate to a specially crafted URL.

#### Details The WebUI error message renders `ExceptionMessage` (which can contain user-controlled input) as unencoded HTML. Server code that produces the message is in `common.py` - specifically `error_headers -> _error_response -> generate_http_error_flask`, which places `ExceptionMessage` into both response headers and the JSON body. The WebUI client then injects that text into the DOM using unsafe methods (examples in `lib/rucio/web/ui/static/*.js` such as `rule.js`, `request_rule.js`, `list_rules.js`) with `jQuery.html(...)` or equivalent, enabling reflected XSS when an attacker-controlled value is included in an error message (e.g. account, attribute, scope).

### PoC 1) Reflected XSS via account parameter (browse or load URL in WebUI context): ```text https://127.0.0.1:8443/ui/account_rse_usage?account=%3Cimg%20src=x%20onerror=alert(document.cookie)%3E ``` Server response (excerpt): ```http HTTP/1.1 500 INTERNAL SERVER ERROR ExceptionClass: AccountNotFound ExceptionMessage: Account <img src=x onerror=alert(document.cookie)> does not exist Content-Type: application/octet-stream

{"ExceptionClass":"AccountNotFound","ExceptionMessage":"Account <img src=x onerror=alert(document.cookie)> does not exist"} ```

**XSS payload triggering…