Biconomy: Nexus
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HardhatFoundry
30,000 USDC
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Submission Details
Severity: low
Invalid

Nexus Smart Accounts is not compliant with ERC-7579

zukanopro

Vulnerability Details

In the Nexuscontract, in the fallback function, if calltype is static, it will call to handlercontract by using staticcall:

fallback() external payable override(Receiver) receiverFallback {
FallbackHandler storage $fallbackHandler = _getAccountStorage().fallbacks[msg.sig];
address handler = $fallbackHandler.handler;
CallType calltype = $fallbackHandler.calltype;
require(handler != address(0), MissingFallbackHandler(msg.sig));
​
if (calltype == CALLTYPE_STATIC) {
assembly {
calldatacopy(0, 0, calldatasize())
​
// The msg.sender address is shifted to the left by 12 bytes to remove the padding
// Then the address without padding is stored right after the calldata
mstore(calldatasize(), shl(96, caller()))
​
if iszero(staticcall(gas(), handler, 0, add(calldatasize(), 20), 0, 0)) { // <---
returndatacopy(0, 0, returndatasize())
revert(0, returndatasize())
}
returndatacopy(0, 0, returndatasize())
return(0, returndatasize())
}
}
. . . . . .
}

But in EIP-7579 link, If the smart account has a fallback handler installed, it MUST use call to invoke the fallback handler. This will lead to unexpected result when using staticcall instead of call

Impact

Contract are not compliant with ERC-7579, and will lead to unexpected result because of using staticcall instead of call.

Tools Used

Manual review

Recommendations

Using call instead of staticcall

Updates

Lead Judging Commences

0xnevi Lead Judge 12 months ago
Submission Judgement Published
Invalidated
Reason: Other
Assigned finding tags:

finding-ERC7579-fallback-staticcall

Invalid, although ERC7579 is violated, staticcall is a desired supported fallback call type as seen in the [documentation](https://github.com/bcnmy/nexus/wiki/Execution-Framework#key-concepts), and there will be no exploit possible

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