Improper Handling of Structural Elements

Instead of treating structured data as a single, opaque block, secure applications must parse and validate its individual structural elements. Attackers exploit this weakness by manipulating these internal elements—like altering a file's magic number, corrupting a packet's sequence field, or injecting malicious data into XML attributes—to bypass validation, crash the system, or trigger unexpected behavior. This flaw often stems from a mismatch between the application's simplified data model and the actual complexity of the format it processes. To prevent it, developers should use robust, well-maintained parsing libraries for known formats, implement strict validation for every field in the structure, and design error-handling routines that safely reject malformed data without exposing internal state.