CVE-2017-8760 in FTA
Summary
by MITRE
An issue was discovered on Accellion FTA devices before FTA_9_12_180. There is XSS in courier/1000@/index.html with the auth_params parameter. The device tries to use internal WAF filters to stop specific XSS Vulnerabilities. However, these can be bypassed by using some modifications to the payloads, e.g., URL encoding.
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Analysis
by VulDB Data Team • 09/24/2020
The vulnerability identified as CVE-2017-8760 affects Accellion FTA (File Transfer Appliance) devices running versions prior to FTA_9_12_180, representing a critical cross-site scripting weakness that undermines the device's security posture. This flaw resides within the courier/1000@/index.html component where the auth_params parameter fails to properly sanitize user input, creating an avenue for malicious actors to inject arbitrary script code into the application's response. The vulnerability specifically exploits the device's insufficient web application firewall filtering mechanisms that were designed to prevent common XSS attack patterns but prove inadequate against sophisticated payload modifications.
The technical exploitation of this vulnerability demonstrates a classic bypass scenario where attackers can circumvent existing security controls through simple yet effective techniques such as URL encoding. This modification allows malicious payloads to evade the internal WAF filters that normally would block known XSS patterns, highlighting a fundamental weakness in the device's security architecture. The vulnerability operates at the application layer where user-supplied parameters are directly incorporated into the HTTP response without proper sanitization or encoding, making it susceptible to script injection attacks that can execute within the context of a user's browser session.
The operational impact of this vulnerability extends beyond simple data theft or session hijacking, as it enables attackers to manipulate the device's functionality and potentially gain unauthorized access to sensitive file transfer operations. An attacker could craft malicious URLs containing encoded XSS payloads that, when visited by an authenticated user, would execute scripts within the victim's browser context. This could lead to full compromise of the file transfer appliance, allowing unauthorized file access, modification of transfer configurations, or even complete system takeover depending on the privileges of the victim user. The vulnerability affects the device's integrity and availability by potentially disrupting legitimate file transfer operations and compromising the confidentiality of data being processed through the appliance.
Organizations utilizing affected Accellion FTA devices should immediately implement mitigation strategies including applying the vendor-provided security patches, enhancing monitoring of suspicious user activities, and implementing additional network-level protections such as enhanced WAF rules that specifically target encoded XSS payloads. The vulnerability aligns with CWE-79 which describes cross-site scripting flaws in web applications, and maps to ATT&CK technique T1059.007 for scripting languages, particularly highlighting the need for proper input validation and output encoding. Security teams should also consider implementing network segmentation to limit access to the appliance, conducting thorough penetration testing to verify the effectiveness of mitigations, and establishing incident response procedures specifically addressing XSS vulnerabilities in file transfer systems. The vulnerability serves as a reminder of the critical importance of robust input validation and the limitations of relying solely on WAF-based protections without proper application-level security controls.