GHSA-4w26-8p97-f4jp AugAssign evaluation order causing OOB write within the object in Vyper

• PyPI vyper: < 0.4.1 → fixed in 0.4.1

Vyper handles AugAssign statements by first caching the target location to avoid double evaluation. However, in the case when target is an access to a DynArray and the rhs modifies the array, the cached target will evaluate first, and the bounds check will not be re-evaluated during the write portion of the statement. In other words, the following code ```vyper def poc(): a: DynArray[uint256, 2] = [1, 2] a[1] += a.pop() ``` is equivalent to: ```vyper def poc(): a: DynArray[uint256, 2] = [1, 2] a[1] += a[len(a) - 1] a.pop() ``` rather than: ```vyper def poc(): a: DynArray[uint256, 2] = [1, 2] s: uint256 = a[1] t: uint256 = a.pop() a[1] = s + t # reverts due to oob access ```