It was discovered that the Western Digital My Cloud is affected by an authentication bypass vulnerability. A malicious person can, therefore, gain full admin access to the disk via the web portal without having to use a password, thereby gaining full control of the My Cloud device.
The Exploitee.rs independently discovered and disclosed the same vulnerability. This vulnerability was successfully verified on a Western Digital My Cloud model WDBCTL0020HWT running firmware version 2.30.172. This issue is not limited to the model that was used to find this vulnerability since most of the products in the My Cloud series share the same (vulnerable) code.
There is currently no fix available.
Introduction
Western Digital My Cloud is a low-cost entry-level network-attached storage device. It was discovered that the Western Digital My Cloud is affected by an authentication bypass vulnerability that allows an unauthenticated user to create an admin session that is tied to her IP address. By exploiting this issue an unauthenticated attacker can run commands that would normally require admin privileges and gain complete control of the My Cloud device. The issue was discovered while reverse engineering the CGI binaries to look for security issues.
Details
Whenever an admin authenticates, a server-side session is created that is bound to the user's IP address. After the session is created it is possible to call authenticated CGI modules by sending the cookie username=admin in the HTTP request. The invoked CGI will check if a valid session is present and bound to the user's IP address.
It was found that it is possible for an unauthenticated attacker to create a valid session without requiring to authenticate. The network_mgr.cgi CGI module contains a command called cgi_get_ipv6 that starts an admin session that is tied to the IP address of the user making the request when invoked with the parameter flag equal to 1. Subsequent invocation of commands that would normally require admin privileges are now authorized if an attacker sets the username=admin cookie.
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