OffbyoneÜberläufe

OffbyoneÜberläufe, often shortened to OBOE, refers to a specific type of integer overflow vulnerability that occurs when a program incorrectly handles the boundary conditions of a numerical operation. This happens when a calculation results in a value that is exactly one unit beyond the maximum representable value for a given integer type, or one unit below the minimum representable value.

The "off-by-one" aspect highlights that the error is not a large, catastrophic overflow, but rather a subtle miscalculation by a single increment or decrement. This can arise from using less than operators (<) instead of less than or equal to (<=), or greater than operators (>) instead of greater than or equal to (>=), in loop conditions or array indexing. For example, a loop intended to iterate ten times might iterate nine or eleven times if the termination condition is off by one.

Such vulnerabilities can have various consequences depending on the context. In array access, an off-by-one error can lead to reading from or writing to adjacent memory locations, potentially corrupting data or causing a crash. In security-sensitive applications, this could be exploited to gain unauthorized access or execute arbitrary code. In less critical applications, it might manifest as incorrect calculations or unexpected program behavior. Detecting and preventing OBOE requires careful attention to loop bounds, array indexing, and the precise use of comparison operators.