CVE-2016-5092 in FortiWeb
Summary
by MITRE
Directory traversal vulnerability in Fortinet FortiWeb before 5.5.3 allows remote authenticated administrators with read and write privileges to read arbitrary files by leveraging the autolearn feature.
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Analysis
by VulDB Data Team • 02/24/2019
The CVE-2016-5092 vulnerability represents a critical directory traversal flaw in Fortinet FortiWeb web application firewalls prior to version 5.5.3. This vulnerability specifically targets the autolearn feature, which is designed to automatically learn and adapt to legitimate traffic patterns for improved security policy enforcement. The flaw arises from insufficient input validation and path sanitization within the autolearn functionality, allowing authenticated attackers with read and write privileges to exploit the system's file handling mechanisms. The vulnerability exists at the application layer where user-supplied input is improperly processed, creating an opportunity for attackers to manipulate file paths and access unauthorized system resources.
The technical implementation of this vulnerability stems from inadequate validation of file paths within the autolearn feature's processing pipeline. When administrators utilize the autolearn functionality to analyze traffic patterns, the system accepts user-provided data without proper sanitization or restriction of directory traversal sequences such as ../ or ..\ prefixes. This allows attackers to craft malicious requests that bypass normal file access controls and traverse the file system to access sensitive files. The vulnerability specifically affects the FortiWeb's configuration management and log file processing components where the autolearn feature operates, creating a direct path to arbitrary file reading capabilities. The flaw aligns with CWE-22 directory traversal weakness, which is categorized under the broader category of path traversal vulnerabilities in web applications.
Operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with access to critical system files, configuration data, and potentially sensitive business information stored within the FortiWeb appliance. Remote authenticated administrators with read and write privileges can leverage this vulnerability to access log files, configuration files, and other system resources that should remain protected. The implications include potential exposure of administrative credentials, network configurations, and application-specific data that could be used for further exploitation or lateral movement within the network. This vulnerability compromises the integrity of the FortiWeb appliance's security posture and could lead to complete system compromise if sensitive files containing authentication tokens or encryption keys are accessed. The attack vector requires authentication but does not necessitate elevated privileges, making it particularly dangerous in environments where administrative accounts may be compromised.
Mitigation strategies for CVE-2016-5092 focus primarily on upgrading to Fortinet FortiWeb version 5.5.3 or later, which includes proper input validation and path sanitization measures. Organizations should implement strict access controls and principle of least privilege to limit the number of authenticated administrators with write privileges. Network segmentation and monitoring should be enhanced to detect unusual file access patterns that might indicate exploitation attempts. The vulnerability can be addressed through configuration changes that restrict the autolearn feature's file system access, implementing additional input validation, and deploying web application firewalls that can detect and block directory traversal attempts. Security teams should also conduct regular vulnerability assessments and penetration testing to identify similar weaknesses in other network security appliances and web applications. This vulnerability demonstrates the importance of proper input validation in security-critical applications and aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as exploitation may involve crafting malicious payloads to traverse file systems. Organizations should also consider implementing file integrity monitoring solutions to detect unauthorized access to critical system files and maintain audit logs for forensic analysis.