Integer overflow vulnerability exists in SimplCommerce at commit 230310c8d7a0408569b292c5a805c459d47a1d8f in the shopping cart functionality. The issue lies in the quantity parameter in the CartController's AddToCart method.
The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.