Vyper is a pythonic Smart Contract Language for the Ethereum virtual machine. In versions 0.3.10 and prior, using the `create_from_blueprint` builtin can result in a double eval vulnerability when `raw_args=True` and the `args` argument has side-effects. It can be seen that the `_build_create_IR` function of the `create_from_blueprint` builtin doesn't cache the mentioned `args` argument to the stack. As such, it can be evaluated multiple times (instead of retrieving the value from the stack). No vulnerable production contracts were found. Additionally, double evaluation of side-effects should be easily discoverable in client tests. As such, the impact is low. As of time of publication, no fixed versions exist.

Affected: PyPI: vyper

### Summary Using the `create_from_blueprint` builtin can result in a double eval vulnerability when `raw_args=True` and the `args` argument has side-effects.

A contract search was performed and no vulnerable contracts were found in production. In particular, the `raw_args` variant of `create_from_blueprint` was not found to be used in production.

### Details It can be seen that the `_build_create_IR` function of the `create_from_blueprint` builtin doesn't cache the mentioned `args` argument to the stack: https://github.com/vyperlang/vyper/blob/cedf7087e68e67c7bfbd47ae95dcb16b81ad2e02/vyper/builtins/functions.py#L1847

As such, it can be evaluated multiple times (instead of retrieving the value from the stack).

### PoC The vulnerability is demonstrated in the following `boa` test: ``` vyper src1 = """ c: uint256 """ deployer = """ created_address: public(address) deployed: public(uint256)

@external def get() -> Bytes[32]: self.deployed += 1 return b''

@external def create_(target: address): self.created_address = create_from_blueprint(target, raw_call(self, method_id("get()"), max_outsize=32), raw_args=True, code_offset=3) """

Factory = b.loads_partial(src1) c = Factory.deploy_as_blueprint()

c2 = b.loads(deployer, b'') c2.create_(c) c2.deployed() ``` The output of `c2.deployed()` is `2` although `create_` was called only once and the value was initialized to `0`.

### Patches Patched in https://github.com/vyperlang/vyper/pull/3976.

### Impact No vulnerab…

Affected: PyPI: vyper

Vyper is a pythonic Smart Contract Language for the Ethereum virtual machine. In versions 0.3.10 and prior, using the `create_from_blueprint` builtin can result in a double eval vulnerability when `raw_args=True` and the `args` argument has side-effects. It can be seen that the `_build_create_IR` function of the `create_from_blueprint` builtin doesn't cache the mentioned `args` argument to the stack. As such, it can be evaluated multiple times (instead of retrieving the value from the stack). No vulnerable production contracts were found. Additionally, double evaluation of side-effects should be easily discoverable in client tests. As such, the impact is low. As of time of publication, no fixed versions exist.