CVE-2017-8794 in FTA
Summary
by MITRE
An issue was discovered on Accellion FTA devices before FTA_9_12_180. Because a regular expression (intended to match local https URLs) lacks an initial ^ character, courier/web/1000@/wmProgressval.html allows SSRF attacks with a file:///etc/passwd#https:// URL pattern.
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Analysis
by VulDB Data Team • 09/24/2020
The vulnerability identified as CVE-2017-8794 affects Accellion FTA devices running versions prior to FTA_9_12_180, representing a significant server-side request forgery flaw that enables unauthorized access to internal system resources. This issue stems from improper input validation within the web application's URL handling mechanism, specifically within the courier/web/1000@/wmProgressval.html component. The vulnerability's root cause lies in a regular expression pattern that fails to include the initial ^ character, which is essential for anchoring the pattern to the beginning of the string. This omission creates a critical security gap that allows attackers to manipulate URL parsing behavior and bypass intended security restrictions.
The technical implementation of this vulnerability demonstrates a classic regular expression denial of service pattern where the lack of proper anchoring permits malicious input to match partial URL patterns rather than complete ones. When an attacker crafts a URL using the file:///etc/passwd#https:// pattern, the malformed regular expression fails to properly validate the URL structure, allowing the application to interpret the request as a legitimate local resource access attempt. This flaw directly enables attackers to perform server-side request forgery attacks by leveraging the application's trust in URL validation mechanisms, potentially accessing sensitive local files and system information that should remain protected from external access.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with the capability to enumerate system resources and potentially escalate privileges within the affected environment. The ability to access /etc/passwd through the file:// protocol demonstrates that attackers can bypass traditional network-based security controls and directly access local file systems, which aligns with attack patterns documented in the attack technique MITRE ATT&CK framework under T1083 - File and Directory Discovery. This vulnerability represents a critical weakness in the application's input validation controls and demonstrates poor secure coding practices that violate fundamental security principles outlined in CWE-20 - Improper Input Validation, where inadequate validation of input data leads to security flaws.
Organizations utilizing Accellion FTA devices must implement immediate mitigations to address this vulnerability, including upgrading to the patched FTA_9_12_180 version or applying the appropriate security patches provided by Accellion. Network segmentation and firewall rules should be implemented to restrict access to the affected web components, while additional monitoring should be deployed to detect suspicious URL patterns and potential exploitation attempts. The vulnerability highlights the importance of proper regular expression implementation and input validation in web applications, emphasizing the need for comprehensive security testing including penetration testing and code reviews to identify similar flaws in other components. Security teams should also consider implementing web application firewalls and input sanitization measures to provide additional layers of protection against similar server-side request forgery attacks that could exploit similar validation weaknesses in other applications.