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GHSA-x2c2-q32w-4w6m
No affected components available
Summary
Vyper compiler allows passing a value in builtin raw_call even if the call is a delegatecall or a staticcall. But in the context of delegatecall and staticcall the handling of value is not possible due to the semantics of the respective opcodes, and vyper will silently ignore the value= argument.
A contract search was performed and no vulnerable contracts were found in production.
Details
The IR for raw_call is built in the RawCall class:
https://github.com/vyperlang/vyper/blob/9136169468f317a53b4e7448389aa315f90b95ba/vyper/builtins/functions.py#L1100
However, the compiler doesn't validate that if either delegatecall or staticall are provided as kwargs, that value wasn't set. For example, the following compiles without errors:
raw_call(self, call_data2, max_outsize=255, is_delegate_call=True, value=msg.value/2)
Impact
If the semantics of the EVM are unknown to the developer, he could suspect that by specifying the value kwarg, exactly the given amount will be sent along to the target. However in fact, no value will be sent.
Here is an example of an potentially problematic implementation of multicall utilizing the raw_call built-in:
value_accumulator: uint256 = empty(uint256)
results: DynArray[Result, max_value(uint8)] = []
return_data: Bytes[max_value(uint8)] = b""
success: bool = empty(bool)
for batch in data:
msg_value: uint256 = batch.value
value_accumulator = unsafe_add(value_accumulator, msg_value)
if (batch.allow_failure == False):
return_data = raw_call(self, batch.call_data, max_outsize=255, value=msg_value, is_delegate_call=True)
success = True
results.append(Result({success: success, return_data: return_data}))
else:
success, return_data = \
raw_call(self, batch.call_data, max_outsize=255, value=msg_value, is_delegate_call=True, revert_on_failure=False)
results.append(Result({success: success, return_data: return_data}))
assert msg.value == value_accumulator, "Multicall: value mismatch"
return results
Patches
Fixed in https://github.com/vyperlang/vyper/pull/3755
Workarounds
Is there a way for users to fix or remediate the vulnerability without upgrading?
References
Are there any links users can visit to find out more?
The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the integrity of the data. There is a low impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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