CVE-2021-40868

Vulnerability

Cloudron 6.2 is vulnerable to reflected cross-site scripting (XSS) in the returnTo parameter on the login page. An attacker can inject arbitrary JavaScript code into the login URL, which will be executed in the context of the victim's browser when the page loads [1][2]. The affected version is Cloudron 6.2 [1][2].

Exploitation

An attacker must craft a malicious login URL containing a JavaScript payload in the returnTo parameter (e.g., ?returnTo=javascript:alert(1)). The victim needs to click on the crafted link. No authentication or special privileges are required to trigger the vulnerability [1][2]. The injected script executes in the user's session on the Cloudron dashboard domain.

Impact

Successful exploitation allows the attacker to execute arbitrary JavaScript in the victim's browser within the Cloudron application context. This can lead to session hijacking, theft of authentication cookies, or defacement of the login page, depending on the payload [1][2]. The attacker does not gain direct access to the server or its data, but can perform actions on behalf of the authenticated user if the user is logged in at the time of exploitation.

Mitigation

As of the available references, Cloudron has not released a fixed version for this vulnerability [1][2]. The Cloudron website (accessed October 2024) promotes regular updates and security fixes, but no specific patch or workaround is described for this issue [3]. Users should monitor official Cloudron channels for a future update and consider limiting exposure by restricting access to the login page until a fix is available.