CVE-2017-9523 in Web Appliance
Summary
by MITRE
The Sophos Web Appliance before 4.3.2 has XSS in the FTP redirect page, aka NSWA-1342.
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Analysis
by VulDB Data Team • 12/26/2020
The Sophos Web Appliance represents a critical security gateway solution designed to protect enterprise networks through web filtering, content inspection, and threat prevention capabilities. This appliance serves as a central point of control for managing network traffic and enforcing security policies across organizations. The vulnerability identified as CVE-2017-9523 specifically affects versions prior to 4.3.2 and resides within the FTP redirect page functionality of the web interface. This particular component handles redirection requests for file transfer protocol communications and serves as an entry point for users accessing FTP resources through the appliance's web interface.
The technical flaw manifests as a cross-site scripting vulnerability in the FTP redirect page implementation, allowing malicious actors to inject arbitrary JavaScript code into the web interface. This vulnerability occurs when the appliance fails to properly sanitize user-supplied input parameters that are subsequently reflected in the redirect page without adequate output encoding or validation. The flaw enables attackers to craft malicious URLs containing script payloads that execute within the context of authenticated sessions, potentially compromising user browsers and the appliance's administrative interface. The vulnerability specifically affects the appliance's handling of FTP redirect parameters, where user input is directly incorporated into HTML responses without proper sanitization mechanisms.
The operational impact of this vulnerability extends beyond simple script execution, as it can be leveraged for privilege escalation and session hijacking attacks. An attacker could potentially craft malicious redirect URLs that, when clicked by an authenticated user, would execute malicious scripts to steal session cookies, modify user permissions, or even redirect users to phishing sites. The vulnerability particularly affects administrators who may inadvertently click on malicious links while browsing FTP resources, potentially leading to complete compromise of the appliance's administrative interface. This creates a significant risk for enterprise environments where the appliance serves as a critical security control, as successful exploitation could allow attackers to bypass web filtering policies and gain unauthorized access to network resources.
Mitigation strategies for this vulnerability require immediate implementation of the vendor-provided security patch version 4.3.2, which addresses the input sanitization issues in the FTP redirect page functionality. Organizations should also implement network segmentation to limit access to the appliance's administrative interface and establish monitoring procedures to detect anomalous redirect behavior. The vulnerability aligns with CWE-79 Cross-site Scripting, which specifically addresses the failure to sanitize user input in web applications, and maps to ATT&CK technique T1059.007 Command and Scripting Interpreter: JavaScript, as it enables attackers to execute malicious JavaScript code within user browsers. Additional defensive measures include implementing Content Security Policy headers to limit script execution and conducting regular security assessments of web applications to identify similar input validation vulnerabilities that could compromise security controls.