Summary

• The Verifier incorrectly calculates the storage slot for balance_of_self, leading to incorrect price calculations and systemic protocol risks.

Vulnerability Details

The Verifier assumes balance_of_self is stored in an ERC20-style balanceOf mapping and uses keccak256(abi.encode(18, scrvUSD)) to compute its slot.

Reality: In the Vyper-based scrvUSD Vault, balance_of_self is a struct member (PriceParams struct) stored at a fixed sequential slot (e.g., slot 12).

• Vyper stores struct members in sequential slots (no hashing):

• The Verifier’s hashing logic (keccak(18, scrvUSD)) points to an arbitrary slot, resulting in garbage data being read.

Impact

• The verifier will provide incorrect scrvUSD price updates to the oracle.

• This can lead to significant financial losses for users relying on the oracle's accuracy.

• The entire price feed system becomes unreliable.

Tools Used

Manual Code Review

Recommendations

Update Verifier Logic:

• Replace the current keccak256-based calculation with direct slot access.

Use Fixed Slot for balance_of_self:

• Directly read balance_of_self from its fixed slot (e.g., slot 12) instead of hashing.

  uint256 balanceOfSelf = getStorageAt(scrvUSDAddress, 12);