Headline
CVE-2022-24845: external calls are not clamped in certain complex expressions
Vyper is a pythonic Smart Contract Language for the ethereum virtual machine. In affected versions, the return of <iface>.returns_int128() is not validated to fall within the bounds of int128. This issue can result in a misinterpretation of the integer value and lead to incorrect behavior. As of v0.3.0, <iface>.returns_int128() is validated in simple expressions, but not complex expressions. Users are advised to upgrade. There is no known workaround for this issue.
Impact
in the following code, the return of <iface>.returns_int128() is not validated to fall within the bounds of int128. as of v0.3.0, <iface>.returns_int128() is validated in simple expressions, but not complex expressions.
interface iface: def returns_int128() -> int128: view def returns_Bytes33() -> Bytes[33]: view
x: iface
@external def call_out(): x: int128 = self.x.returns_int128() # affected, <0.3.0 y: uint256 = convert(self.x.returns_int128(), uint256) # affected, <0.3.2 z: Bytes[33] = concat(self.x.returns_Bytes33(), b"") # affected >= 0.3.0, <0.3.2
Patches
0.3.2 (as of 049dbdc)
Workarounds
Break up operations involving external calls into multiple statements. For instance, instead of the example above, use
x: int128 = self.x.returns_int128()
y: uint256 = convert(x, uint256)