The server lacks thread safety and can be crashed by anomalous data sent by an anonymous user from a remote network. The crash causes the FTP service to become unavailable, affecting all users and processes that rely on it for file transfers. If the crash occurs during file upload or download, it could lead to incomplete file transfers, potentially corrupting data. The repeated crash might also affect the stability of the underlying system, especially if it leads to resource leaks or affects other services.
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
A race condition occurs within concurrent environments, and it is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:
A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.