Susan has noticed that a web application used by her company does not always handle multithreading properly, particularly when multiple threads access the same variable. This could allow an attacker who realized this vulnerability to exploit it and crash the server. What type of issue has Susan found?

Susan has found a race condition. A race condition is a bug in a multithreaded program that can occur when two or more threads are accessing the same variable at the same time and the outcome of the program depends on the order in which the threads access the variable.
In Susan's case, the race condition could occur when two threads are both trying to update the same variable. If the threads are not synchronized, then it is possible for one thread to update the variable before the other thread has finished reading it. This could lead to the variable being in an inconsistent state, which could cause the program to crash.
Race conditions can be difficult to find and fix, but there are a number of techniques that can be used to prevent them. One common technique is to use locks to synchronize access to shared variables. Locks ensure that only one thread can access a variable at a time, which prevents race conditions from occurring.
A buffer overflow is characterized by the attempt to insert more data into a buffer than it can accommodate.
A logic bomb is a type of malware that carries out its malicious activity when a specific logical condition is met. Improper error handling, as the name implies, refers to a lack of sufficient or suitable error-handling mechanisms within the software.