CVE-2018-17153 in My Cloud
Summary
by MITRE
It was discovered that the Western Digital My Cloud device through 2.30.x is affected by an authentication bypass vulnerability. An unauthenticated attacker can exploit this vulnerability to authenticate as an admin user without needing to provide a password, thereby gaining full control of the device. (Whenever an admin logs into My Cloud, 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 a login. The network_mgr.cgi CGI module contains a command called "cgi_get_ipv6" that starts an admin session -- tied to the IP address of the user making the request -- if the additional parameter "flag" with the value "1" is provided. Subsequent invocation of commands that would normally require admin privileges now succeed if an attacker sets the username=admin cookie.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 03/25/2020
The vulnerability identified as CVE-2018-17153 represents a critical authentication bypass flaw in Western Digital My Cloud devices running firmware versions up to 2.30.x. This security weakness fundamentally undermines the device's access control mechanisms by allowing unauthenticated attackers to escalate privileges and gain administrative control without providing valid credentials. The flaw exists within the device's session management system and specifically targets the network_mgr.cgi CGI module, which serves as a critical entry point for privilege escalation attacks.
The technical implementation of this vulnerability stems from improper session validation within the My Cloud device's web interface. When legitimate administrators log into the device, the system creates server-side sessions that are bound to the user's IP address for security purposes. However, the vulnerability exploits a design flaw in the network_mgr.cgi module where the cgi_get_ipv6 command can be manipulated to create administrative sessions without proper authentication. This occurs when the attacker provides the flag parameter with a value of "1" to the cgi_get_ipv6 command, which triggers session creation tied to the attacker's IP address. Once this unauthorized session is established, the attacker can leverage the administrative privileges by simply setting the username=admin cookie in subsequent HTTP requests to any authenticated CGI modules.
The operational impact of this vulnerability is severe and far-reaching, as it provides attackers with complete administrative control over affected devices. This level of access enables unauthorized users to modify device configurations, access stored data, install malicious software, and potentially use the compromised device as a pivot point for attacking other systems within the network. The vulnerability's exploitation does not require any special privileges or complex attack vectors, making it particularly dangerous for enterprise and home users who may not have robust network security measures in place. The ease of exploitation means that attackers can compromise devices remotely without needing physical access or prior knowledge of valid credentials.
From a cybersecurity perspective, this vulnerability aligns with CWE-287, which addresses improper authentication issues in software systems. The flaw demonstrates poor input validation and session management practices that violate fundamental security principles. According to MITRE ATT&CK framework, this vulnerability maps to T1078 - Valid Accounts and T1566 - Phishing, as it allows attackers to bypass authentication mechanisms and gain access to legitimate administrative accounts through session manipulation. Organizations should implement immediate mitigations including firmware updates from Western Digital, network segmentation to limit access to affected devices, and monitoring for suspicious cookie usage patterns. Additionally, network administrators should consider implementing firewall rules to restrict access to the affected CGI modules and regularly audit device configurations to ensure that unauthorized administrative sessions are not established.
The vulnerability highlights the importance of proper session management and authentication controls in embedded web applications. Device manufacturers must implement robust validation mechanisms that prevent unauthorized session creation and ensure that all administrative operations require proper authentication before proceeding. This flaw serves as a reminder that even seemingly simple web interface components can contain critical security vulnerabilities when proper input validation and session management controls are not implemented. The affected Western Digital My Cloud devices represent a significant risk to users who may not regularly update their firmware, as the vulnerability remains exploitable in older firmware versions that are no longer receiving security updates.