CVE-2017-7281 in Enterprise Backup
Summary
by MITRE
An issue was discovered in Unitrends Enterprise Backup before 9.1.2. A lack of sanitization of user input in the createReportName and saveReport functions in recoveryconsole/bpl/reports.php allows for an authenticated user to create a randomly named file on disk with a user-controlled extension, contents, and path, leading to remote code execution, aka Unrestricted File Upload.
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Analysis
by VulDB Data Team • 08/30/2020
The vulnerability identified as CVE-2017-7281 resides within the Unitrends Enterprise Backup software version 9.1.1 and earlier, representing a critical security flaw that enables authenticated attackers to achieve remote code execution through improper input validation. This issue manifests in the recoveryconsole/bpl/reports.php component where the createReportName and saveReport functions fail to adequately sanitize user-provided input parameters. The absence of proper input sanitization creates a path traversal and file upload vulnerability that can be exploited by malicious actors who have gained authentication access to the system.
The technical implementation of this vulnerability stems from the software's failure to validate and sanitize file names and paths provided by users during report creation processes. When an authenticated user submits data through the report creation interface, the application directly incorporates user input into file system operations without proper validation or sanitization. This allows attackers to manipulate the file naming and path parameters to create arbitrary files with user-controlled extensions and contents, effectively bypassing normal file upload restrictions. The vulnerability specifically enables attackers to upload files with executable extensions such as .php, .asp, or .jsp, which can then be executed on the server to provide remote code execution capabilities.
From an operational perspective, this vulnerability presents a severe risk to organizations using Unitrends Enterprise Backup systems, as it allows authenticated attackers to gain full control over the backup server. The impact extends beyond simple file manipulation to include complete system compromise, data exfiltration, and potential lateral movement within the network. Attackers can leverage this vulnerability to establish persistent backdoors, install malware, or use the compromised system as a launch point for attacks against other network resources. The vulnerability's classification as an unrestricted file upload issue aligns with CWE-434, which specifically addresses the danger of uploading files without proper validation of their contents or extensions.
The exploitation of this vulnerability requires only authenticated access to the system, making it particularly dangerous as it can be leveraged by insiders or attackers who have obtained legitimate credentials through phishing, credential theft, or other social engineering techniques. The attack vector follows the typical pattern of command and control operations where attackers first gain access to the backup system and then use the file upload capability to deploy malicious payloads. This vulnerability directly maps to ATT&CK technique T1105, which covers the use of file transfer protocols for command and control communications, and T1059, which addresses the execution of malicious code through various system interfaces.
Organizations should immediately implement mitigations including upgrading to Unitrends Enterprise Backup version 9.1.2 or later, which contains the necessary patches to address the input sanitization issues. Additional protective measures include implementing strict file type validation, restricting file upload capabilities to only trusted extensions, and conducting regular security audits of file system operations. Network segmentation and access control measures should be strengthened to limit the potential impact of successful exploitation, while monitoring systems should be configured to detect unusual file creation patterns or attempts to upload executable files. The vulnerability serves as a reminder of the critical importance of input validation and the potential consequences of inadequate sanitization of user-provided data in web applications.