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Submission Details
Severity: medium
Invalid

Hardcoded Storage Slots Vulnerability

binaryreturns

Description:

The ScrvusdVerifier contracts use hardcoded storage slots to extract state from the scrvUSD contract.

If the scrvUSD contract is upgraded or its storage layout changes (which is common in contract upgrades), these hardcoded slot numbers would point to incorrect or completely different data.

The verifier would then extract incorrect values, leading to invalid price calculations and updates.

Root Cause:

This creates tight coupling between the verifier contracts and the specific implementation of the scrvUSD contract.

Impact:

If the scrvUSD contract is upgraded or its storage layout changes , the verifier contracts would extract incorrect data, leading to invalid price updates.

code

// From ScrvusdVerifierV1.sol
function verifyScrvusdByBlockHash(
bytes memory _block_header_rlp,
bytes memory _proof_rlp
) external returns (uint256) {
Verifier.BlockHeader memory block_header = Verifier.parseBlockHeader(_block_header_rlp);
require(block_header.hash != bytes32(0), "Invalid blockhash");
require(
block_header.hash == IBlockHashOracle(BLOCK_HASH_ORACLE).get_block_hash(block_header.number),
"Blockhash mismatch"
);
​
uint256[PARAM_CNT] memory params = _extractParametersFromProof(block_header.stateRootHash, _proof_rlp);
return _updatePrice(params, block_header.timestamp, block_header.number);
}
​
function verifyScrvusdByStateRoot(
uint256 _block_number,
bytes memory _proof_rlp
) external returns (uint256) {
bytes32 state_root = IBlockHashOracle(BLOCK_HASH_ORACLE).get_state_root(_block_number);
​
uint256[PARAM_CNT] memory params = _extractParametersFromProof(state_root, _proof_rlp);
// Use last_profit_update as the timestamp surrogate
return _updatePrice(params, params[5], _block_number);
}
​

recommendation

Consider using interfaces or getter functions instead of hardcoded storage slots.

Updates

Lead Judging Commences

0xnevi Lead Judge 5 months ago
Submission Judgement Published
Invalidated
Reason: Out of scope
Assigned finding tags:

[invalid] finding-upgradeable-verifier-contracts

Invalid, - srCRVUSD is a minimal proxy, meaning it can never by upgraded, see [here](https://www.cyfrin.io/blog/upgradeable-proxy-smart-contract-pattern#:~:text=Minimal%20proxies%20are%20distinct%20from,provide%20upgrade%20or%20authorization%20functionality.) and [here](https://www.rareskills.io/post/eip-1167-minimal-proxy-standard-with-initialization-clone-pattern) for more info. - Even if srcrvUSD is migrated in the future via a new minimal proxy contract deployment (which is highly unlikely), the verifier contracts can be migrated along with it via revoking the access-control within the `ScrvusdOracleV2.vy` and then granting access to a new oracle. This is also not within the scope of this contest.

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