Type-confusion is a memory-safety bug where software treats a value, object, or pointer as the wrong kind of data. For example, a program may assume a structure contains one layout or a numeric value, when it actually contains something else. That mismatch can make later reads and writes target the wrong memory, causing corruption, crashes, or in some cases code execution.
In cyber security, type-confusion matters because it is a common weakness in browser engines, file parsers, and other complex code that processes untrusted input. Attackers often look for it in JavaScript engines and JIT compilers, where a small logic mistake can undermine bounds checks or object handling. Defenders reduce the risk with fuzzing, strict validation, safer memory practices, exploit mitigations, and sandboxing, but a reachable type-confusion bug is still a serious target when exposed to attacker-controlled data.