Security Experts:

Multiple Flaws Patched in WD MyCloud Device Firmware

Vulnerabilities that could allow unauthorized file deletion, unauthorized command execution and authentication bypass impacted WD (Western Digital) MyCloud devices, Trustwave reports. 

The vulnerabilities were discovered in the MyCloud personal storage device and were reported to Western Digital last year. The company has already released a firmware update to address them. 

All of the issue were found by Trustwave security researcher Martin Rakhmanov in the nas_sharing.cgi binary. 

The first of them was the inclusion of hardcoded credentials in the binary, which could allow anyone to authenticate to the device. 

The hardcoded username was "mydlinkBRionyg" and represents an issue that other security researchers observed as well. Earlier this year, GulfTech’s James Bercegay revealed that this admin user can be used with password “abc12345cba” as a backdoor that could be turned into a root shell. D-Link devices were previously impacted by the same issue. 

The nas_sharing.cgi binary, Rakhmanov discovered, would also allow any user to execute shell commands as root. An attacker looking to exploit the issue can use the “artist” parameter to execute a command to create a file, for example. 

The same faulty binary can be used for arbitrary file deletion, an operation possible through manipulating the “path” parameter, the security researcher says. A command using the “path” parameter can be passed using base64 encoding, the same as with the “artist” parameter.

Rakhmanov explains that “usually on embedded systems many processes run unrestricted (i.e. as root) so no security checks are performed at all once a command (file deletion in this case) is about to execute.” 

Trustwave’s researcher also published proof of concept code that combines the hardcoded credential issue with command execution and arbitrary file deletion, respectively. 

Western Digital apparently resolved these issues with the release of firmware version 2.30.172 a couple of months ago. 

The update patched a SMB server (samba) security vulnerability (CVE-2017-7494), along with “critical security vulnerabilities that potentially allowed unauthorized file deletion, unauthorized command execution and authentication bypass,” the company revealed in the release notes (PDF). 

Related: Hardcoded Backdoor Found on Western Digital Storage Devices

Related: Multiple Zero-days Disclosed in Western Digital NAS Storage Devices

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