CVE-2023-32675 — Nonpayable default functions are sometimes payable in vyper

Affected: vyperlang vyper

Vyper is a pythonic Smart Contract Language for the ethereum virtual machine. In contracts with more than one regular nonpayable function, it is possible to send funds to the default function, even if the default function is marked `nonpayable`. This applies to contracts compiled with vyper versions prior to 0.3.8. This issue was fixed by the removal of the global `calldatasize` check in commit `02339dfda`. Users are advised to upgrade to version 0.3.8. Users unable to upgrade should avoid use of nonpayable default functions.

GHSA-vxmm-cwh2-q762 — Vyper's nonpayable default functions are sometimes payable

Affected: PyPI: vyper

### Impact in contracts with at least one regular nonpayable function, due to the callvalue check being inside of the selector section, it is possible to send funds to the default function by using less than 4 bytes of calldata, even if the default function is marked `nonpayable`. this applies to contracts compiled with vyper<=0.3.7. ```vyper # @version 0.3.7

# implicitly nonpayable @external def foo() -> uint256: return 1

# implicitly nonpayable @external def __default__(): # could receive ether here pass ```

### Patches this was fixed by the removal of the global calldatasize check in https://github.com/vyperlang/vyper/commit/02339dfda0f3caabad142060d511d10bfe93c520.

### Workarounds don't use nonpayable default functions

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CVE-2023-32675 — Nonpayable default functions are sometimes payable in vyper

GHSA-vxmm-cwh2-q762 — Vyper's nonpayable default functions are sometimes payable