CVE-2021-40103 in Concrete
Summary
by MITRE • 09/27/2021
An issue was discovered in Concrete CMS through 8.5.5. Path Traversal can lead to Arbitrary File Reading and SSRF.
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Analysis
by VulDB Data Team • 10/02/2021
The vulnerability identified as CVE-2021-40103 affects Concrete CMS versions through 8.5.5 and represents a critical path traversal flaw that enables attackers to perform arbitrary file reading and server-side request forgery operations. This vulnerability resides within the content management system's handling of file paths and URL parameters, creating a dangerous attack surface that can be exploited by malicious actors to gain unauthorized access to sensitive system files and potentially compromise the entire server infrastructure.
The technical implementation of this vulnerability stems from insufficient input validation and sanitization within Concrete CMS's file handling mechanisms. Attackers can manipulate URL parameters or file path inputs to traverse the directory structure and access files that should remain protected within the system's file hierarchy. This flaw specifically manifests when the application processes user-supplied input without proper validation, allowing malicious path sequences such as ../ or ../../ to bypass normal access controls and retrieve files from arbitrary locations on the server filesystem. The vulnerability operates at the application layer and can be exploited through HTTP requests that contain crafted path traversal sequences, making it particularly dangerous as it requires minimal privileges to exploit and can be executed remotely.
The operational impact of CVE-2021-40103 extends beyond simple file reading capabilities to include potential server-side request forgery attacks that can be leveraged to access internal services or systems. An attacker exploiting this vulnerability can read configuration files, database credentials, application source code, and other sensitive information that may lead to complete system compromise. The path traversal aspect allows for reading system files such as password hashes, configuration files, and potentially even system binaries, while the SSRF component can enable attackers to make requests to internal services that are normally not accessible from the internet. This dual nature of the vulnerability makes it particularly dangerous as it can be used to escalate privileges and move laterally within network environments, potentially leading to full system compromise and data exfiltration.
Organizations using Concrete CMS versions 8.5.5 and earlier should immediately implement mitigations to address this vulnerability. The primary defense mechanism involves applying the vendor-provided patches and updates that correct the input validation flaws in the file handling components. Additionally, implementing proper input sanitization at the application level can help prevent path traversal attacks by filtering out dangerous sequences in user-supplied input. Network-level protections such as web application firewalls can also provide additional layers of defense by detecting and blocking malicious path traversal patterns in HTTP requests. Security teams should conduct thorough audits of their Concrete CMS installations to identify any potential exposure and implement proper access controls to limit the impact of potential exploitation attempts. This vulnerability aligns with CWE-22 Path Traversal and CWE-918 Server-Side Request Forgery, and can be mapped to ATT&CK techniques including T1059 Command and Scripting Interpreter and T1566 Phishing to understand the full attack surface and potential lateral movement capabilities.
The broader implications of this vulnerability highlight the critical importance of proper input validation and secure coding practices in content management systems. Organizations should establish robust security testing procedures that include penetration testing and code review processes to identify similar vulnerabilities before they can be exploited by malicious actors. Regular security updates and patch management programs should be implemented to ensure that all components of the web application stack remain protected against known vulnerabilities. The vulnerability demonstrates how seemingly simple flaws in file handling can create significant security risks that can be exploited to gain unauthorized access to critical system resources and sensitive data.