CVE-2021-21799 in R-SeeNet
Summary
by MITRE • 07/16/2021
Cross-site scripting vulnerabilities exist in the telnet_form.php script functionality of Advantech R-SeeNet v 2.4.12 (20.10.2020). If a user visits a specially crafted URL, it can lead to arbitrary JavaScript code execution in the context of the targeted user’s browser. An attacker can provide a crafted URL to trigger this vulnerability.
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Analysis
by VulDB Data Team • 07/19/2021
The vulnerability identified as CVE-2021-21799 represents a critical cross-site scripting flaw within the Advantech R-SeeNet network management platform version 2.4.12, released on October 20, 2020. This vulnerability specifically affects the telnet_form.php script functionality, which serves as an interface for telnet connection management within the web-based administration console. The flaw stems from inadequate input validation and output encoding mechanisms that fail to properly sanitize user-supplied data before rendering it in web pages, creating an environment where malicious script execution can occur. The vulnerability is particularly concerning as it allows remote code execution through web-based attacks without requiring authentication or privileged access to the system.
The technical implementation of this XSS vulnerability occurs when the telnet_form.php script processes user input parameters without sufficient sanitization measures. When a user navigates to a maliciously crafted URL containing specially formatted JavaScript code within the request parameters, the vulnerable application fails to properly encode or escape the input before incorporating it into the HTML response. This allows the malicious payload to execute within the victim's browser context with the privileges of the authenticated user. The vulnerability is classified as a reflected XSS attack pattern where the malicious script is reflected back to the user through the web application's response, leveraging the trust relationship between the browser and the application. According to CWE taxonomy, this represents a CWE-79: Improper Neutralization of Input During Web Page Generation, which is a fundamental weakness in web application security. The vulnerability also aligns with ATT&CK technique T1566.001: Phishing for Information through crafted web content and T1203: Exploitation for Client Execution through browser-based attack vectors.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with the capability to perform session hijacking, steal user credentials, manipulate data, and potentially escalate privileges within the network management environment. An attacker could craft URLs that redirect users to malicious sites, steal session cookies, or inject additional malicious code that persists across user sessions. The vulnerability affects any user who accesses the vulnerable R-SeeNet web interface, making it particularly dangerous in enterprise environments where multiple administrators may interact with the system. The attack vector requires only that a user clicks on a malicious link, making it highly exploitable in social engineering campaigns. Organizations using this version of R-SeeNet are at risk of unauthorized access to their network management systems, potentially leading to complete compromise of the monitored network infrastructure. The vulnerability's exploitation does not require special privileges or complex attack chains, making it a high-risk exposure that could be leveraged for significant network infiltration.
Mitigation strategies for CVE-2021-21799 should prioritize immediate remediation through the vendor-provided security patches and updates. Organizations should implement comprehensive input validation and output encoding measures across all web application components, particularly those handling user-supplied data. The implementation of Content Security Policy headers can provide additional defense-in-depth measures to prevent unauthorized script execution, while regular security assessments and web application firewalls should be deployed to detect and block malicious requests. Network segmentation and access controls should be implemented to limit exposure of the vulnerable system to untrusted networks. The vulnerability highlights the importance of maintaining up-to-date security patches and conducting regular vulnerability assessments of network management systems. Organizations should also implement user education programs to recognize and report suspicious links, as the attack relies heavily on social engineering techniques to deliver malicious payloads. Regular monitoring of network traffic for suspicious patterns and implementing automated vulnerability scanning tools can help identify potential exploitation attempts before they succeed. The remediation process should include thorough testing of security patches in controlled environments before deployment to production systems to ensure compatibility and prevent service disruptions.