CVE-2021-40928 in FlexTV
Summary
by MITRE • 10/02/2021
Cross-site scripting (XSS) vulnerability in index.php in FlexTV beta development version allows remote attackers to inject arbitrary web script or HTML via the PHP_SELF parameter.
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Analysis
by VulDB Data Team • 10/08/2021
The vulnerability identified as CVE-2021-40928 represents a critical cross-site scripting flaw within the FlexTV beta development version, specifically affecting the index.php script. This vulnerability resides in the handling of the PHP_SELF parameter, which is a server variable containing the path to the current script. The flaw enables remote attackers to inject malicious web scripts or HTML code through this parameter, creating a persistent security risk for affected systems. The vulnerability classification aligns with CWE-79, which specifically addresses Cross-Site Scripting vulnerabilities, making it a well-documented and dangerous exposure in web application security contexts.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious payload and submits it through the PHP_SELF parameter in the index.php script. The web application fails to properly sanitize or validate this input before rendering it in the response, allowing the injected script to execute within the victim's browser context. This creates a dangerous scenario where attackers can perform actions such as stealing session cookies, redirecting users to malicious sites, or executing arbitrary commands on behalf of authenticated users. The vulnerability is particularly concerning because it affects a core application file and leverages a parameter that is commonly used in web applications for various purposes.
The operational impact of this vulnerability extends beyond simple script injection, as it can lead to complete compromise of user sessions and potential data breaches. Attackers can exploit this weakness to hijack user sessions, modify application behavior, or redirect users to phishing sites designed to capture credentials. The beta development version context suggests this vulnerability may have been present in pre-release software, indicating a potential gap in security testing and quality assurance processes. Organizations using this software face significant risks, particularly if the application handles sensitive user data or provides administrative functions that could be exploited through session hijacking or privilege escalation attacks.
Mitigation strategies for CVE-2021-40928 should focus on implementing proper input validation and output encoding mechanisms. The most effective immediate solution involves sanitizing all user inputs, particularly the PHP_SELF parameter, by removing or encoding potentially dangerous characters before processing. This approach aligns with ATT&CK technique T1068, which covers local privilege escalation, as proper input validation prevents malicious code execution. Organizations should also implement Content Security Policy headers to limit script execution sources, apply proper HTML escaping when rendering dynamic content, and consider using web application firewalls to detect and block malicious payloads. Additionally, the vulnerability highlights the importance of comprehensive security testing during development phases, including automated scanning and manual penetration testing, to identify and remediate such flaws before deployment. Regular security updates and patches should be implemented immediately upon availability to address this and similar vulnerabilities in web applications.