M4: Insufficient Input/Output Validation (2024)

Missing or weak validation of user inputs and server responses, leading to injection attacks, XSS, or data corruption in mobile apps.

Risk Assessment

Am I Vulnerable?

• Lack of Input Validation: Failure to properly validate user input can expose the application to injection attacks like SQL injection, command injection, or XSS.
• Inadequate Output Sanitization: Insufficient sanitization of output data can result in XSS vulnerabilities, allowing attackers to inject and execute malicious scripts.
• Context-Specific Validation Neglect: Neglecting to consider specific validation requirements based on data context can create vulnerabilities, such as path traversal attacks or unauthorized access to files.
• Insufficient Data Integrity Checks: Not performing proper data integrity checks can lead to data corruption or unauthorized modification, compromising reliability and security.
• Poor Secure Coding Practices: Neglecting secure coding practices, such as using parameterized queries or escaping/encoding data, contributes to input/output validation vulnerabilities.

How Do I Prevent It?

• Input Validation: Validate and sanitize user input strictly. Implement length restrictions and reject unexpected or malicious data.
• Output Sanitization: Properly sanitize output data to prevent cross-site scripting (XSS) attacks and use encoding techniques when displaying or transmitting data.
• Context-Specific Validation: Execute validation based on data context to prevent path traversal or injection attacks.
• Data Integrity Checks: Implement checks to detect and prevent data corruption or unauthorized modifications.
• Secure Coding Practices: Follow secure coding practices, such as using parameterized queries and prepared statements to prevent SQL injection.
• Regular Security Testing: Conduct regular assessments including penetration testing and code reviews to identify and address vulnerabilities.

Example Attack Scenarios

• Remote Code Execution via Malicious Input: An attacker identifies a mobile application lacking proper input validation and sanitization. By crafting a malicious input containing unexpected characters, they exploit the application's behavior. Due to insufficient validation, the application mishandles the input, leading to vulnerabilities. The attacker successfully executes arbitrary code, gaining unauthorized access to the device's resources and sensitive data.
• Injection Attacks via Insufficient Output Validation: An attacker identifies a mobile application with inadequate output validation and sanitization. They exploit an entry point where user-generated content or untrusted data is processed. By crafting malicious input containing code or scripts (e.g., HTML, JavaScript, SQL), the attacker takes advantage of the lack of output validation. The application fails to validate or sanitize the submitted input, allowing the execution of injected code or unintended operations.
• Remote Code Execution via Malformed Output: An attacker identifies a mobile application that processes user-provided data and generates dynamic output. The attacker crafts specially formatted data that exploits the application's insufficient output validation. The application fails to properly validate or sanitize the generated output, allowing the attacker's crafted data to execute code or trigger unintended actions, gaining control over the mobile device, its resources, or sensitive data.