CVE-2021-21804 in R-SeeNet
Summary
by MITRE • 07/16/2021
A local file inclusion (LFI) vulnerability exists in the options.php script functionality of Advantech R-SeeNet v 2.4.12 (20.10.2020). A specially crafted HTTP request can lead to arbitrary PHP code execution. An attacker can send a crafted HTTP request to trigger this vulnerability.
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Analysis
by VulDB Data Team • 07/19/2021
The vulnerability CVE-2021-21804 represents a critical local file inclusion flaw within Advantech R-SeeNet version 2.4.12, which was released on October 20, 2020. This security weakness resides in the options.php script functionality, making it a prime target for attackers seeking to compromise the affected system. The vulnerability classification aligns with CWE-98, which specifically addresses the inclusion of files without proper validation, allowing attackers to execute arbitrary code on the target system. The flaw exists due to inadequate input sanitization and validation mechanisms within the web application's file handling processes, creating an exploitable condition that can be leveraged for unauthorized access and system compromise.
The technical exploitation of this vulnerability occurs through a carefully crafted HTTP request that manipulates the options.php script to include and execute arbitrary PHP files. Attackers can leverage this weakness to bypass normal access controls and execute malicious code with the privileges of the web server process. The vulnerability enables an attacker to read arbitrary files from the server filesystem, potentially accessing sensitive configuration data, user credentials, or other confidential information. This type of attack falls under the ATT&CK technique T1566.001 for Phishing with Malicious Attachments and T1059.007 for Command and Scripting Interpreter: PowerShell, though the primary vector is through web-based file inclusion. The exploitation process typically involves sending a specially crafted request that includes a payload designed to traverse directory structures and include malicious files, effectively allowing remote code execution.
The operational impact of CVE-2021-21804 extends beyond simple code execution, as it provides attackers with persistent access to the compromised system. Once exploited, an attacker can establish backdoors, escalate privileges, and potentially use the compromised system as a pivot point for attacking other networked devices. The vulnerability affects the integrity and confidentiality of the Advantech R-SeeNet system, which is commonly used for network monitoring and security management. Organizations relying on this software for critical infrastructure monitoring face significant risk, as the compromise could lead to complete system takeover and unauthorized access to network traffic monitoring capabilities. The vulnerability also impacts availability by potentially allowing attackers to disrupt services through code execution or file manipulation.
Mitigation strategies for CVE-2021-21804 should focus on immediate patching and implementation of proper input validation controls. Organizations must update their Advantech R-SeeNet installations to the latest available version that addresses this vulnerability, as provided by the vendor. Network segmentation and access controls should be implemented to limit exposure of the affected system to untrusted networks. Web application firewalls can help detect and block malicious requests attempting to exploit this vulnerability. Input validation should be strengthened to prevent directory traversal attacks, and proper file inclusion mechanisms should be implemented using allowlists rather than dynamic inclusion. Security monitoring should include detection of suspicious HTTP requests targeting the options.php script, and regular security assessments should be conducted to identify similar vulnerabilities in other applications. The remediation process should also include reviewing and updating the system's security posture, implementing principle of least privilege, and conducting security awareness training for personnel managing the affected systems.