CVE-2020-5203 in Fat-Free Framework
Summary
by MITRE
In Fat-Free Framework 3.7.1, attackers can achieve arbitrary code execution if developers choose to pass user controlled input (e.g., $_REQUEST, $_GET, or $_POST) to the framework's Clear method.
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Analysis
by VulDB Data Team • 04/13/2024
The Fat-Free Framework vulnerability CVE-2020-5203 represents a critical security flaw that enables remote code execution through improper input validation in the framework's Clear method. This vulnerability specifically affects version 3.7.1 of the Fat-Free Framework, a popular PHP micro-framework used for building web applications. The issue arises when developers inadvertently pass user-controlled data from superglobal arrays such as $_REQUEST, $_GET, or $_POST directly into the Clear method without adequate sanitization or validation. The vulnerability is classified under CWE-94, which describes "Improper Control of Generation of Code ('Code Injection')" and aligns with ATT&CK technique T1190 for "Exploit Public-Facing Application" and T1059.007 for "Command and Scripting Interpreter: PowerShell" as attackers can leverage this flaw to execute arbitrary commands on the server.
The technical exploitation of this vulnerability occurs because the Clear method in the Fat-Free Framework does not properly validate or sanitize input parameters before processing them. When user input flows directly into this method, it can be interpreted as executable code rather than mere data, allowing attackers to inject malicious payloads that get executed within the context of the web application. This creates a pathway for attackers to gain unauthorized access to the server, potentially leading to complete system compromise. The flaw is particularly dangerous because it leverages common PHP practices where developers often pass request parameters directly to framework methods without proper input filtering, making it a widespread issue across applications using this framework version.
The operational impact of CVE-2020-5203 extends beyond simple code execution to encompass full system compromise and data breach potential. Attackers can leverage this vulnerability to upload malicious files, establish backdoors, escalate privileges, or perform lateral movement within network environments. The vulnerability affects any application using Fat-Free Framework 3.7.1 that passes user input to the Clear method, making it particularly concerning for web applications that process user submissions or handle external data inputs. Organizations running affected applications face significant risk of unauthorized access, data exfiltration, and potential service disruption, as the vulnerability can be exploited remotely without authentication. This aligns with ATT&CK tactics including TA0006 for "Credential Access" and TA0008 for "Lateral Movement" when attackers use the compromised system as a foothold for further attacks.
Mitigation strategies for CVE-2020-5203 require immediate action including upgrading to a patched version of the Fat-Free Framework where the vulnerability has been resolved. Organizations should also implement input validation and sanitization practices that prevent user-controlled data from reaching framework methods without proper filtering. The principle of least privilege should be enforced by ensuring that web applications run with minimal required permissions and that all user inputs are properly validated before processing. Additionally, implementing web application firewalls and intrusion detection systems can help detect and prevent exploitation attempts. Security teams should conduct thorough code reviews to identify all instances where framework methods receive unvalidated user input, particularly focusing on methods that handle request parameters. Regular security assessments and vulnerability scanning should be implemented to identify similar issues in other framework components or custom code that may present analogous security risks.