CVE-2023-3545 in LMS
Summary
by MITRE • 11/28/2023
Improper sanitisation in `main/inc/lib/fileUpload.lib.php` in Chamilo LMS <= v1.11.20 on Windows and Apache installations allows unauthenticated attackers to bypass file upload security protections and obtain remote code execution via uploading of `.htaccess` file. This vulnerability may be exploited by privileged attackers or chained with unauthenticated arbitrary file write vulnerabilities, such as CVE-2023-3533, to achieve remote code execution.
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Analysis
by VulDB Data Team • 12/17/2023
The vulnerability described in CVE-2023-3545 represents a critical security flaw in the Chamilo Learning Management System version 1.11.20 and earlier, specifically affecting Windows environments with Apache web servers. This issue stems from inadequate input sanitization within the file upload functionality, creating a pathway for malicious actors to circumvent established security measures. The vulnerability's exploitation potential is particularly concerning as it allows unauthenticated attackers to bypass file upload restrictions and execute arbitrary code on the target system.
The technical implementation of this flaw occurs within the fileUpload.lib.php library file, where insufficient validation and sanitization of uploaded file names and content permits attackers to manipulate the upload process. The specific mechanism involves the ability to upload .htaccess files which can contain malicious directives that alter server behavior and potentially enable code execution. This vulnerability is particularly dangerous because it operates at the web server configuration level, where .htaccess files can modify server settings and execute code through specific directives like php_value or php_flag that can change execution contexts. The improper sanitization creates a direct path for attackers to inject malicious content that the server will process as legitimate configuration instructions.
The operational impact of this vulnerability extends beyond simple unauthorized file uploads, as it can lead to complete system compromise when combined with other vulnerabilities. Attackers can leverage this flaw to establish persistent access, escalate privileges, or deploy additional malicious payloads within the target environment. The vulnerability's chaining potential with CVE-2023-3533 demonstrates how seemingly isolated flaws can create cascading security risks, where one vulnerability enables the exploitation of another. This type of vulnerability directly violates the principle of least privilege and can result in unauthorized access to sensitive educational data, user credentials, and system resources. The attack surface is particularly wide given that Chamilo LMS is commonly deployed in educational environments where system administrators may not always maintain strict security monitoring.
Security mitigation strategies should focus on immediate patching of the affected Chamilo LMS versions to address the sanitization issues in the file upload library. Organizations should implement comprehensive file upload validation mechanisms that enforce strict content type checking, filename sanitization, and directory restrictions. The implementation of web application firewalls and security monitoring systems can help detect and prevent exploitation attempts. Additionally, organizations should conduct thorough security assessments of their web applications to identify similar sanitization flaws in other components. This vulnerability aligns with CWE-20, which describes improper input validation, and represents a clear violation of the principle that all user-provided data must be validated and sanitized before processing. The ATT&CK framework categorizes this as a technique for "Upload File" and "Command and Scripting Interpreter" where attackers can leverage file upload capabilities to execute malicious code on target systems, emphasizing the need for robust input validation and access controls.