CVE-2021-22951 in Concrete
Summary
by MITRE • 11/19/2021
Unauthorized individuals could view password protected files using view_inline in Concrete CMS (previously concrete 5) prior to version 8.5.7. Concrete CMS now checks to see if a file has a password in view_inline and, if it does, the file is not rendered.For version 8.5.6, the following mitigations were put in place a. restricting file types for view_inline to images only b. putting a warning in the file manager to advise users.Credit for discovery: "Solar Security Research Team"Concrete CMS security team CVSS scoring is 5.3: AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:NThis fix is also in Concrete version 9.0.0
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Analysis
by VulDB Data Team • 11/25/2021
The vulnerability identified as CVE-2021-22951 represents a critical access control flaw in Concrete CMS versions prior to 8.5.7, where unauthorized users could bypass password protection mechanisms to access files marked with password restrictions. This issue stems from the view_inline functionality within the content management system, which was designed to display files directly within web pages without requiring separate download actions. The flaw allowed attackers to exploit this feature to view password-protected content, effectively undermining the security controls that administrators had implemented to protect sensitive files. The vulnerability demonstrates a fundamental failure in authentication and authorization checks within the file handling system, creating a pathway for information disclosure that directly violates security principles.
The technical implementation of this vulnerability resides in the insufficient validation of file access controls within the view_inline function. When Concrete CMS processes requests for inline file viewing, the system failed to properly verify whether the requested file was protected by a password or other access restrictions. This oversight allowed the system to render password-protected files through the inline viewer, bypassing the intended access control mechanisms. The flaw specifically affected the file rendering process where the system would check file properties but not properly enforce access restrictions when the view_inline feature was invoked. This represents a classic case of inadequate input validation and access control enforcement, aligning with CWE-285: Improper Authorization and CWE-352: Cross-Site Request Forgery patterns in security vulnerabilities.
The operational impact of this vulnerability extends beyond simple information disclosure, as it fundamentally compromises the integrity of file access controls within the Concrete CMS platform. Attackers could potentially access sensitive documents, confidential business information, or proprietary content that was intended to be protected through password restrictions. The CVSS score of 5.3 indicates a medium severity vulnerability with network access required but no user interaction needed, making it particularly dangerous as it can be exploited remotely without requiring user engagement. This vulnerability affects organizations that rely on Concrete CMS for content management, where unauthorized access to protected files could result in data breaches, compliance violations, and reputational damage. The issue impacts both version 8.5.6 and earlier versions, with the fix being implemented in version 8.5.7 and subsequently in version 9.0.0, demonstrating the importance of timely security updates in content management systems.
The Concrete CMS security team addressed this vulnerability through multiple mitigation strategies implemented in version 8.5.6. The primary fix involved restricting the file types that could be processed through the view_inline function to images only, effectively limiting the scope of the vulnerability. Additionally, the file manager was updated to include warning messages that alert users about the security implications of using inline viewing for protected files. These mitigations align with ATT&CK technique T1213.002: Data from Information Repositories, where adversaries attempt to access protected data through system vulnerabilities. The security team's approach demonstrates a layered defense strategy, combining technical fixes with user awareness measures to prevent exploitation. The vulnerability was discovered by the Solar Security Research Team, highlighting the importance of external security research in identifying and reporting system weaknesses. Organizations using Concrete CMS should prioritize updating to version 8.5.7 or later to ensure protection against this specific access control bypass vulnerability, as the fix addresses both the immediate technical flaw and provides additional safeguards through user interface warnings and restricted functionality.