Inheritable Smart Contract Wallet

Summary

The removeBeneficiary function uses the delete operator to remove beneficiaries, which replaces the address with address(0) rather than removing the array element. This can lead to funds being distributed to the zero address during inheritance, effectively burning those funds.

Vulnerability Details

When removing a beneficiary, the function replaces the address with address(0) instead of properly removing the element from the array:

This creates several issues:

1. The zero address remains in the beneficiaries array

2. During fund distribution in withdrawInheritedFunds, tokens or ETH will be sent to the zero address

3. The divisor used to calculate shares remains unchanged

Impact

This vulnerability could lead to:

1. Permanently lost funds when distributed to the zero address

2. Incorrect calculation of inheritance shares

3. Potential denial of service if many addresses are removed, as the array maintains its original length

4. Unexpected behavior in other functions that rely on the beneficiaries array

This is rated as medium severity because it can lead to permanent loss of funds during inheritance distribution, but requires specific actions (removing a beneficiary without replacing them) to trigger.

Tools Used

Manual code review

Recommendations

Implement a proper array element removal technique that preserves array integrity:

This approach maintains array integrity, ensures no zero addresses in the beneficiaries list, and properly resets the deadline to maintain the security model.