CVE-2019-9955 in ATP500
Summary
by MITRE
On Zyxel ATP200, ATP500, ATP800, USG20-VPN, USG20W-VPN, USG40, USG40W, USG60, USG60W, USG110, USG210, USG310, USG1100, USG1900, USG2200-VPN, ZyWALL 110, ZyWALL 310, ZyWALL 1100 devices, the security firewall login page is vulnerable to Reflected XSS via the unsanitized 'mp_idx' parameter.
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Analysis
by VulDB Data Team • 10/22/2024
The vulnerability identified as CVE-2019-9955 affects a range of Zyxel network security devices including ATP200, ATP500, ATP800, USG series firewalls, and ZyWALL models. This represents a critical security flaw in the authentication interface of these enterprise-grade firewalls that could potentially allow attackers to execute malicious scripts within the context of authenticated sessions. The vulnerability specifically resides in the firewall login page implementation where user input is not properly sanitized before being reflected back to the browser, creating an environment conducive to cross-site scripting attacks. The affected devices operate as network security appliances that typically serve as the first line of defense for enterprise networks, making this vulnerability particularly concerning from a security perspective.
The technical flaw manifests through the unsanitized 'mp_idx' parameter that is processed within the firewall's web-based management interface. When an attacker crafts a malicious URL containing a crafted payload in the mp_idx parameter and tricks a user into clicking it, the malicious script gets executed in the victim's browser session. This reflected XSS vulnerability occurs because the web application fails to properly validate and sanitize user-supplied input before incorporating it into the response sent back to the browser. The vulnerability is classified as CWE-79 - Cross-site Scripting and aligns with ATT&CK technique T1059.007 - Command and Scripting Interpreter: PowerShell, as it enables attackers to execute malicious code within the browser context of authenticated users. The impact is amplified because these devices typically require administrative privileges to access, meaning successful exploitation could provide attackers with elevated access to critical network infrastructure.
The operational impact of this vulnerability extends beyond simple script execution as it represents a potential gateway for more sophisticated attacks within enterprise environments. An attacker could leverage this vulnerability to steal session cookies, redirect users to malicious sites, or inject malicious content that could compromise the integrity of the firewall management interface. Given that these devices are network security appliances, successful exploitation could lead to unauthorized access to network traffic monitoring, configuration changes, or even complete network compromise. The vulnerability affects multiple generations of Zyxel firewalls, indicating a widespread issue across the product line that could impact numerous organizations simultaneously. Organizations using these devices may face potential data breaches, network disruption, and compliance violations if the vulnerability is exploited, particularly in regulated industries where network security is paramount.
Mitigation strategies for this vulnerability should include immediate firmware updates from Zyxel as the primary remediation approach, as the vendor would have likely released patches addressing the XSS flaw in the web interface. Network administrators should also implement additional security controls such as web application firewalls that can detect and block malicious payloads targeting reflected XSS vulnerabilities. Access controls should be strengthened by limiting direct web access to firewall management interfaces and implementing multi-factor authentication where possible. Regular security assessments should be conducted to identify other potential XSS vulnerabilities within network infrastructure components, as this type of flaw often indicates broader input validation issues. Organizations should also monitor for indicators of compromise related to these specific device models and implement network segmentation to limit the potential impact if exploitation occurs. The vulnerability serves as a reminder of the critical importance of input validation in web applications, particularly in security-critical interfaces where unauthorized access could result in significant operational and security consequences.