CVE-2022-29255

Vyper is a Pythonic Smart Contract Language for the ethereum virtual machine. In versions prior to 0.3.4 when a calling an external contract with no return value, the contract address (including side effects) could be evaluated twice. This may result in incorrect outcomes for contracts. This issue has been addressed in v0.3.4.

### Impact when a calling an external contract with no return value, the contract address could be evaluated twice. this is usually only an efficiency problem, but if evaluation of the contract address has side effects, it could result in double evaluation of the side effects. in the following example, `Foo(msg.sender).bar()` is the contract address for the following call (to `.foo()`), and could get evaluated twice ```vyper interface Foo: def foo(): nonpayable def bar() -> address: nonpayable @external def do_stuff(): Foo(Foo(msg.sender).bar()).foo() ``` ### Patches 6b4d8ff185de071252feaa1c319712b2d6577f8d ### Workarounds assign contract addresses to variables. the above example would change to ```vyper @external def do_stuff(): t: Foo = Foo(msg.sender).bar() t.foo() ``` ### References ### For more information

Vyper es un Lenguaje de Contratos Inteligentes de Python para la máquina virtual de Ethereum. En versiones anteriores a 0.3.4, cuando es llamado a un contrato externo sin valor de retorno, la dirección del contrato (incluyendo los efectos secundarios) podía ser evaluada dos veces. Esto podía resultar en respuestas incorrectas para los contratos. Este problema ha sido abordado en versión 0.3.4