CVE-2023-42460: Vyper's `_abi_decode` input not validated in complex expressions
(updated )
_abi_decode()
does not validate input when it is nested in an expression. the following example gets correctly validated (bounds checked):
x: int128 = _abi_decode(slice(msg.data, 4, 32), int128)
however, the following example is not bounds checked
@external
def abi_decode(x: uint256) -> uint256:
a: uint256 = convert(_abi_decode(slice(msg.data, 4, 32), (uint8)), uint256) + 1
return a # abi_decode(256) returns: 257
the issue can be triggered by constructing an example where the output of _abi_decode
is not internally passed to make_setter
(an internal codegen routine) or other input validating routine.
References
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