apinit on Cray devices with CLE before 4.2.UP02 and 5.x before 5.1.UP00 does not use alpsauth data to validate the UID in a launch message, which allows local users to gain privileges via a modified aprun program, aka ID FN5912.
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.