Inheritable Smart Contract Wallet

Summary

An edge case in the inherit function allows a random external user to become the owner of the contract.

Vulnerability Details

In line 221(https://github.com/CodeHawks-Contests/2025-03-inheritable-smart-contract-wallet/blob/main/src/InheritanceManager.sol#L221), when the beneficiaries length is 1, any user can become the owner after 90 days. This effectively means that if the previous owner means to pass on ownership to another user, a malicious user can front run this transaction and become contract owner.

Impact

The contract provides the owner with the means to transfer out all funds. Any user can become owner when the beneficiary array length is 1 and drain all funds from the contract.

Tools Used

n/a

Recommendations

This behaviour is presumably used to pass on ownership of the contract to a trusted entity. Since these are the beneficiaries, it is recommended that this code first check that the msg.sender is a beneficiary before passing on the ownership.