CVE-2015-2856 in File Transfer Appliance
Summary
by MITRE
Directory traversal vulnerability in the template function in function.inc in Accellion File Transfer Appliance devices before FTA_9_11_210 allows remote attackers to read arbitrary files via a .. (dot dot) in the statecode cookie.
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Analysis
by VulDB Data Team • 11/23/2019
The CVE-2015-2856 vulnerability represents a critical directory traversal flaw within the Accellion File Transfer Appliance FTA_9_11_210 and earlier versions. This vulnerability exists in the template function implementation within the function.inc file, specifically exposing a dangerous path manipulation weakness in how the system processes the statecode cookie parameter. The flaw enables remote attackers to bypass normal access controls and retrieve arbitrary files from the underlying file system through simple directory traversal sequences using the .. (dot dot) notation. This vulnerability directly impacts the core security architecture of the appliance by undermining the integrity of file access controls and potentially exposing sensitive data stored on the system.
The technical exploitation of this vulnerability occurs through manipulation of the statecode cookie parameter which is processed by the vulnerable template function in function.inc. When the system processes this cookie value without proper input validation or sanitization, it allows attackers to inject directory traversal sequences that navigate outside the intended file access boundaries. The vulnerability stems from inadequate validation of user-supplied input, specifically the statecode cookie value, which is then directly used in file system operations without proper path normalization or access control checks. This weakness creates an unrestricted file access condition that can be leveraged to read files anywhere within the appliance's file system, potentially including configuration files, database files, or other sensitive system data.
The operational impact of CVE-2015-2856 extends beyond simple information disclosure, as it can lead to complete system compromise and data breaches. Remote attackers can exploit this vulnerability to access sensitive system files, configuration data, and potentially user credentials stored within the appliance's file system. The vulnerability affects the fundamental security model of the Accellion appliance, as it allows unauthorized access to system resources that should be protected from external access. This weakness can be particularly devastating in environments where the appliance handles sensitive data transfers, as it may enable attackers to obtain confidential information or gain deeper system access that could facilitate further attacks. The vulnerability also violates core security principles of least privilege and access control enforcement, undermining the appliance's ability to protect its own data and maintain secure file operations.
Organizations affected by this vulnerability should immediately implement mitigation strategies including patching to the latest FTA_9_11_210 release or higher, which contains the necessary fixes for this directory traversal issue. Network segmentation and firewall rules should be implemented to restrict access to the appliance to only trusted sources, while monitoring should be enhanced to detect suspicious cookie values or file access patterns. The vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, and maps to ATT&CK technique T1083 for discovering file and directory permissions. Additional mitigations include implementing input validation for all cookie parameters, deploying web application firewalls to filter malicious traversal sequences, and conducting comprehensive security assessments of the appliance configuration to ensure no other similar vulnerabilities exist within the system's codebase.