CVE-2023-32058 — Vyper vulnerable to integer overflow in loop

2026-10-17T11:33:02.227227+00:00

Affected: vyperlang vyper

Vyper is a Pythonic smart contract language for the Ethereum virtual machine. Prior to version 0.3.8, due to missing overflow check for loop variables, by assigning the iterator of a loop to a variable, it is possible to overflow the type of the latter. The issue seems to happen only in loops of type `for i in range(a, a + N)` as in loops of type `for i in range(start, stop)` and `for i in range(stop)`, the compiler is able to raise a `TypeMismatch` when trying to overflow the variable. The problem has been patched in version 0.3.8.

GHSA-6r8q-pfpv-7cgj — Vyper vulnerable to integer overflow in loop

2026-10-17T11:33:02.227285+00:00

Affected: PyPI: vyper

### Impact

Due to missing overflow check for loop variables, by assigning the iterator of a loop to a variable, it is possible to overflow the type of the latter.

In the following example, calling `test` returns `354`, meaning that the variable `a` did store `354` a value out of bound for the type `uint8`.

```Vyper @external def test() -> uint16: x:uint8 = 255 a:uint8 = 0 for i in range(x, x+100): a = i return convert(a,uint16) ```

The issue seems to happen only in loops of type `for i in range(a, a + N)` as in loops of type `for i in range(start, stop)` and `for i in range(stop)`, the compiler is able to raise a `TypeMismatch` when trying to overflow the variable.

thanks to @trocher for reporting

### Patches

patched in 3de1415ee77a9244eb04bdb695e249d3ec9ed868

### Workarounds

Most recent entries from all

CVE-2023-32058 — Vyper vulnerable to integer overflow in loop

GHSA-6r8q-pfpv-7cgj — Vyper vulnerable to integer overflow in loop