CVE-2017-6908 in concrete5
Summary
by MITRE
An issue was discovered in concrete5 <= 5.6.3.4. The vulnerability exists due to insufficient filtration of user-supplied data (fID) passed to the "concrete5-legacy-master/web/concrete/tools/files/selector_data.php" URL. An attacker could execute arbitrary HTML and script code in a browser in the context of the vulnerable website.
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Analysis
by VulDB Data Team • 12/29/2019
The vulnerability identified as CVE-2017-6908 represents a critical cross-site scripting flaw within the concrete5 content management system version 5.6.3.4 and earlier. This weakness resides in the file selector data tool which processes user input without adequate sanitization, creating an avenue for malicious actors to inject arbitrary HTML and script code into the application's response. The affected endpoint concrete5-legacy-master/web/concrete/tools/files/selector_data.php demonstrates a classic input validation failure where the fID parameter receives insufficient filtration, allowing attackers to manipulate the application's behavior through crafted requests.
The technical exploitation of this vulnerability stems from the application's failure to properly validate and sanitize the fID parameter before incorporating it into the HTTP response. This insufficient filtration creates a direct path for attackers to execute malicious scripts within the context of the vulnerable website, effectively enabling them to perform actions such as stealing user sessions, defacing the website, or redirecting users to malicious sites. The flaw operates under CWE-79 which specifically addresses cross-site scripting vulnerabilities, where the application fails to properly encode or escape user-controllable data before including it in dynamically generated web pages. The vulnerability's impact is amplified by the fact that it affects a core file management tool that is likely accessible to authenticated users, though the exact access requirements would depend on the application's configuration and user permissions.
Operationally, this vulnerability presents significant risks to organizations utilizing concrete5 versions up to 5.6.3.4 as it allows for persistent script injection attacks that can compromise user sessions and potentially escalate to full system compromise. Attackers can leverage this weakness to execute malicious code in the browser context of legitimate users, potentially leading to data theft, privilege escalation, or unauthorized modifications to the website content. The vulnerability's exploitation aligns with ATT&CK technique T1566 which covers social engineering tactics, particularly through malicious file downloads or script execution. Organizations may find their websites defaced or compromised, with users unknowingly executing malicious payloads that can harvest sensitive information or establish backdoor access to the system. The legacy nature of this vulnerability means that many organizations may have outdated systems that have not received security updates, making them particularly susceptible to exploitation.
The recommended mitigation strategy involves immediate upgrading to a patched version of concrete5, as version 5.6.3.5 and later releases contain proper input validation and sanitization measures. Organizations should also implement proper input filtering at the application level, ensuring that all user-supplied data is properly escaped and validated before being processed or returned in HTTP responses. Additional protective measures include implementing content security policies, using web application firewalls to detect and block malicious requests, and conducting regular security assessments to identify similar vulnerabilities in other components of the web application stack. Network-level protections such as intrusion detection systems can also help detect exploitation attempts, while regular monitoring of website content and user access logs should be maintained to identify potential compromise indicators. The vulnerability's classification as a persistent XSS issue underscores the importance of comprehensive security testing and regular patch management procedures to prevent similar weaknesses from being exploited in the application's lifecycle.