An integer underflow during deserialization may allow any unauthenticated user to read out of bounds heap memory. This may result into secret data or pointers revealing the layout of the address space to be included into a deserialized data structure, which may potentially lead to thread crashes or cause denial of service conditions.
The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.