CVE-2017-7282 in Enterprise Backup
Summary
by MITRE
An issue was discovered in Unitrends Enterprise Backup before 9.1.1. The function downloadFile in api/includes/restore.php blindly accepts any filename passed to /api/restore/download as valid. This allows an authenticated attacker to read any file in the filesystem that the web server has access to, aka Local File Inclusion (LFI).
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 09/17/2020
The vulnerability identified as CVE-2017-7282 represents a critical local file inclusion flaw within the Unitrends Enterprise Backup software version 9.1.0 and earlier. This issue stems from inadequate input validation mechanisms within the downloadFile function located in the api/includes/restore.php file. The flaw allows authenticated attackers to manipulate the filename parameter passed through the /api/restore/download endpoint, enabling them to access arbitrary files on the system where the web server has read permissions. This type of vulnerability falls under the common weakness enumeration CWE-22, which specifically addresses improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. The attack vector requires an authenticated user account, making it less likely to be exploited by casual attackers but still poses significant risk to organizations with compromised credentials or insider threats.
The technical implementation of this vulnerability exploits the lack of proper sanitization and validation of user-supplied input within the restore.php file. When an attacker sends a crafted request to the download endpoint, the system processes the filename parameter without adequate checks to ensure it remains within legitimate boundaries. This blind acceptance of filenames allows for manipulation through directory traversal sequences such as ../ or ../../, enabling access to sensitive system files, configuration data, or potentially even database files that contain confidential information. The vulnerability specifically affects the web server's ability to restrict file access based on user permissions, as the system fails to validate whether the requested file path is legitimate or whether it attempts to access restricted directories within the filesystem. The impact is particularly severe because the web server process typically runs with elevated privileges, potentially allowing access to files that would otherwise be protected by the operating system's access control mechanisms.
The operational impact of CVE-2017-7282 extends beyond simple information disclosure, as it provides attackers with potential access to sensitive backup data, system configuration files, and potentially credentials stored within the application's environment. Attackers could leverage this vulnerability to extract database connection strings, API keys, or other authentication tokens that might be stored in accessible files. The vulnerability also enables reconnaissance activities where attackers can map the filesystem structure and identify other potential attack surfaces within the application environment. From an attacker's perspective, this vulnerability aligns with the MITRE ATT&CK technique T1083 for discovering file and directory permissions, and T1005 for data from local system, as it allows for systematic exploration of the victim's filesystem. The threat actor could potentially use this access to escalate privileges or move laterally within the network by obtaining system-level credentials or configuration files that might reveal network architecture details.
Organizations affected by this vulnerability should implement immediate mitigations including upgrading to Unitrends Enterprise Backup version 9.1.1 or later, which contains the necessary patches to address the input validation issue. Additionally, administrators should review and restrict file access permissions for the web server process, ensuring that it operates with the principle of least privilege. Network segmentation and monitoring of API endpoints can help detect anomalous access patterns that might indicate exploitation attempts. The vulnerability also underscores the importance of implementing proper input validation and output encoding practices as recommended by the OWASP Top Ten and other security frameworks. Security teams should conduct thorough audits of all file handling functions within their applications to identify similar vulnerabilities that might allow for unauthorized file access. Regular security assessments and penetration testing should include validation of input sanitization mechanisms to prevent similar path traversal vulnerabilities from being introduced in future development cycles.