Inheritable Smart Contract Wallet

Summary

There's a bug in the onlyBeneficiaryWithIsInherited modifier that can cause an out-of-bounds error when checking if the caller is a beneficiary. The issue comes from an incorrect loop condition, which allows the index to go beyond the length of the beneficiaries array. If this happens, the contract will revert, making functions that use this modifier completely unusable.

Vulnerability Details

Line 53

Notice the +1 in the condition. That means the loop will try to access beneficiaries[i] even when i is out of bounds, causing an immediate revert. As a result:

Beneficiaries won't be able to call certain functions (like buyOutEstateNFT() or appointTrustee()).

Inheritance functions may be completely broken, leaving funds stuck.

Impact

No beneficiary use functions protected by this modifier.

Inheritance assets may become inaccessible forever.

The contract could be unusable after deployment unless fixed.

Tools Used

Foundry

Manual code review

Recommendations

To fix the issue modify the onlyBeneficiaryWithIsInherited modifier to ensure safe array access:

This way, if msg.sender isn’t in the beneficiaries list, it fails gracefully with a proper error message instead of crashing the whole function.