Headline
GHSA-6r8q-pfpv-7cgj: Vyper vulnerable to integer overflow in loop
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.
@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
The problem is patched at https://github.com/vyperlang/vyper/commit/3de1415ee77a9244eb04bdb695e249d3ec9ed868
Workarounds
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.
@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
The problem is patched at vyperlang/vyper@3de1415
Workarounds****References
- GHSA-6r8q-pfpv-7cgj
- https://nvd.nist.gov/vuln/detail/CVE-2023-32058
- vyperlang/vyper@3de1415
Related news
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.