CVE-2017-17550 in ZyWALL USG
Summary
by MITRE
ZyXEL ZyWALL USG 2.12 AQQ.2 and 3.30 AQQ.7 devices are affected by a CSRF vulnerability via a cgi-bin/zysh-cgi cmd action to add a user account. This account's access could, for example, subsequently be used for stored XSS.
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Analysis
by VulDB Data Team • 04/11/2020
The vulnerability identified as CVE-2017-17550 affects ZyXEL ZyWALL USG firewall devices running firmware versions 2.12 AQQ.2 and 3.30 AQQ.7, representing a critical cross-site request forgery weakness that undermines the security posture of network infrastructure. This flaw exists within the web-based administrative interface of the ZyWALL USG devices, specifically in the cgi-bin/zysh-cgi command execution endpoint that handles user account creation operations. The vulnerability stems from insufficient validation of the origin of requests made to the administrative interface, allowing an attacker to craft malicious web pages that can trigger unauthorized administrative actions without the knowledge or consent of legitimate users. This type of vulnerability falls under CWE-352, which specifically addresses Cross-Site Request Forgery conditions in web applications, and aligns with ATT&CK technique T1078.004 for Valid Accounts and T1566.001 for Phishing, as it enables attackers to create unauthorized user accounts and potentially escalate privileges through subsequent exploitation.
The technical implementation of this CSRF vulnerability occurs when an attacker constructs a malicious webpage that includes hidden form submissions or embedded script commands targeting the vulnerable cgi-bin/zysh-cgi endpoint with the cmd action parameter set to add a user account. When a legitimate administrator visits this malicious page while authenticated to the ZyWALL USG interface, the browser automatically submits the forged request to the device's administrative interface, creating a new user account with potentially elevated privileges. This account creation process bypasses normal authentication and authorization mechanisms, as the request appears to originate from a legitimate administrative session. The vulnerability is particularly concerning because the newly created account can be leveraged for persistent access to the device and potentially for executing stored XSS attacks, where malicious scripts can be stored on the device and executed against other users who access the administrative interface. The attack vector exploits the trust relationship between the web browser and the device, leveraging the fact that the device does not properly verify the authenticity of requests originating from external sources.
The operational impact of this vulnerability extends beyond simple unauthorized account creation, as it fundamentally compromises the integrity and confidentiality of the network security infrastructure. An attacker who successfully exploits this CSRF vulnerability can establish persistent access to the ZyWALL USG device, potentially gaining access to sensitive network configuration data, firewall rules, and administrative controls. The ability to create accounts with administrative privileges creates a backdoor that can be used for ongoing surveillance, traffic interception, or modification of security policies. Furthermore, the potential for subsequent stored XSS exploitation amplifies the threat, as the attacker could inject malicious scripts that execute against other administrators or users accessing the device's web interface, leading to session hijacking, data exfiltration, or further compromise of the network. This vulnerability directly impacts the device's ability to maintain secure administrative access and can result in complete compromise of the firewall's security functions, affecting network segmentation, intrusion detection capabilities, and overall network security posture.
Organizations should implement immediate mitigations including network segmentation to isolate critical firewall devices, implementing strict access controls for administrative interfaces, and deploying web application firewalls to detect and block malicious requests targeting the vulnerable endpoints. The firmware vendors should be consulted for security patches and updates that address the CSRF validation weaknesses in the web interface. Additional protective measures include disabling unnecessary administrative web interfaces, implementing multi-factor authentication for administrative access, and conducting regular security assessments of network infrastructure components. The vulnerability demonstrates the importance of proper input validation and request origin verification in web applications, particularly in security-critical devices where unauthorized administrative access can have severe consequences for network security. Organizations should also consider implementing network monitoring solutions that can detect anomalous administrative access patterns and account creation activities that may indicate exploitation attempts. The incident highlights the necessity of maintaining current firmware versions and following security best practices for network infrastructure management, as outdated devices with known vulnerabilities represent significant attack vectors for sophisticated adversaries.