CVE-2022-0734 in USG
Summary
by MITRE • 05/24/2022
A cross-site scripting vulnerability was identified in the CGI program of Zyxel USG/ZyWALL series firmware versions 4.35 through 4.70, USG FLEX series firmware versions 4.50 through 5.20, ATP series firmware versions 4.35 through 5.20, and VPN series firmware versions 4.35 through 5.20, that could allow an attacker to obtain some information stored in the user's browser, such as cookies or session tokens, via a malicious script.
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Analysis
by VulDB Data Team • 05/29/2022
This cross-site scripting vulnerability in Zyxel network security appliances represents a critical weakness in the firmware implementations across multiple product lines including USG/ZyWALL series, USG FLEX series, ATP series, and VPN series. The vulnerability exists within the CGI program component of these devices and affects firmware versions ranging from 4.35 through 5.20 for most series, with the USG FLEX series extending to version 5.20. The flaw stems from inadequate input validation and output sanitization mechanisms within the web interface components that process user-supplied data. This vulnerability is classified under CWE-79 as Cross-Site Scripting, which is a well-documented web application security weakness that allows attackers to inject malicious scripts into web pages viewed by other users. The attack vector specifically targets the web management interfaces of these network devices, making it particularly dangerous as it could be exploited by remote attackers without requiring physical access to the network infrastructure.
The technical exploitation of this vulnerability enables attackers to inject malicious scripts that can execute within the browser context of authenticated users who interact with the affected web interfaces. When a user accesses a compromised web page or interacts with a maliciously crafted request, the injected script can access sensitive information stored in the user's browser such as session cookies, authentication tokens, and potentially other session-related data. This information leakage represents a significant security risk as it could allow attackers to hijack user sessions and gain unauthorized access to the network management interfaces. The vulnerability operates through the standard XSS attack mechanism where malicious input is not properly sanitized before being rendered back to the user, creating an execution environment for attacker-controlled scripts. This type of vulnerability is particularly concerning in network security appliances as these devices typically require high-privilege access and contain sensitive network configuration information.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates a pathway for more sophisticated attacks including session hijacking, privilege escalation, and potential lateral movement within the network infrastructure. Network administrators who access these devices through web interfaces become vulnerable to attacks that could compromise their administrative sessions and potentially allow attackers to modify firewall rules, access network configurations, or perform other administrative functions. The vulnerability affects multiple Zyxel product lines, increasing the potential attack surface and making it more challenging for organizations to implement comprehensive mitigation strategies. Attackers could leverage this vulnerability to establish persistent access to network management interfaces, potentially leading to complete network compromise. This aligns with ATT&CK technique T1566 for initial access through spearphishing with malicious attachments or links, and T1071.004 for application layer protocol usage via web protocols, as the attack exploits web-based management interfaces. The impact is particularly severe because network security appliances are fundamental to network protection, and compromising their management interfaces can undermine the entire security posture of an organization's network infrastructure.
Organizations should prioritize immediate firmware updates from Zyxel to address this vulnerability, as the affected firmware versions span multiple generations and product lines. The mitigation strategy should include implementing network segmentation to limit access to these management interfaces, deploying web application firewalls to detect and block malicious script injection attempts, and conducting thorough network monitoring for suspicious activities related to these devices. Additionally, organizations should enforce strict access controls for network management interfaces, implement multi-factor authentication where possible, and regularly audit access logs for unauthorized attempts to interact with these vulnerable components. The vulnerability demonstrates the importance of secure coding practices and input validation in network device firmware, as well as the necessity for regular security assessments of network infrastructure components. Organizations should also consider implementing network access controls that restrict direct web access to these management interfaces from untrusted networks, and establish procedures for rapid response to similar vulnerabilities in other network security devices within their environment.