CVE-2021-41465 in concrete5-legacy
Summary
by MITRE • 10/02/2021
Cross-site scripting (XSS) vulnerability in concrete/elements/collection_theme.php in concrete5-legacy 5.6.4.0 and below allows remote attackers to inject arbitrary web script or HTML via the rel parameter.
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Analysis
by VulDB Data Team • 10/08/2021
The cross-site scripting vulnerability identified as CVE-2021-41465 affects concrete5-legacy version 5.6.4.0 and earlier, representing a critical security flaw in the content management system's legacy codebase. This vulnerability resides within the concrete/elements/collection_theme.php file, which processes user input related to collection themes and their associated relationships. The flaw specifically manifests when the application fails to properly sanitize the rel parameter, allowing malicious actors to inject arbitrary web scripts or HTML content that can be executed in the context of other users' browsers. The vulnerability demonstrates characteristics consistent with CWE-79, which categorizes cross-site scripting as a code injection flaw where untrusted data is improperly incorporated into web pages without adequate validation or encoding.
The technical exploitation of this vulnerability occurs through the manipulation of the rel parameter within the collection_theme.php script, which serves as a bridge between collection data and theme relationships in the concrete5 framework. Attackers can craft malicious payloads that, when processed by the vulnerable application, execute within the browser context of authenticated users who view the affected content. This creates a persistent threat vector where malicious scripts can steal session cookies, redirect users to phishing sites, or perform unauthorized actions on behalf of victims. The vulnerability's impact is particularly severe because it affects legacy systems that may continue to operate in enterprise environments where security updates are not regularly applied, making it a prime target for exploitation in environments with outdated software configurations.
The operational consequences of this vulnerability extend beyond simple script execution, as it enables attackers to establish persistent footholds within affected systems and potentially escalate privileges. When exploited, the XSS flaw can facilitate session hijacking attacks, allowing unauthorized access to administrative functions and user accounts. The vulnerability also poses significant risks to data integrity and confidentiality, as malicious scripts can capture sensitive information transmitted through the affected web application. Organizations running concrete5-legacy systems are particularly vulnerable because these older versions may not receive security patches, leaving them exposed to this and similar vulnerabilities that have been addressed in newer releases. The attack surface is further expanded by the fact that this vulnerability can be exploited through various vectors including user profile pages, content management interfaces, and any feature that processes the rel parameter in collection theme relationships.
Mitigation strategies for CVE-2021-41465 should prioritize immediate remediation through the application of security patches or upgrades to concrete5-legacy versions 5.6.4.1 or later, which contain fixes for this specific vulnerability. Organizations should implement comprehensive input validation and output encoding mechanisms to prevent similar issues from occurring in other parts of their applications, following the principles outlined in the OWASP Top Ten security guidelines. Network-level protections such as web application firewalls can provide additional defense-in-depth measures, though these should not replace proper code-level fixes. Security teams should conduct thorough vulnerability assessments of their legacy systems to identify other potential XSS vulnerabilities within concrete5 installations and related applications, as the presence of one vulnerability often indicates the possibility of similar flaws. The ATT&CK framework's T1566 technique for "Phishing" and T1059.007 for "Command and Scripting Interpreter" are relevant to understanding how attackers might leverage this vulnerability for initial access and execution within compromised environments. Regular security monitoring and user education about the risks of interacting with untrusted content are essential components of a comprehensive defense strategy against this and similar cross-site scripting threats.