Foundry DeFi Stablecoin CodeHawks Audit Contest
Cyfrin
DeFiFoundry
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Submission Details
Severity: medium
Valid

Incomplete check for stale data from Chainlink Aggregator inside staleCheckLatestRoundData()

t0x1c

Summary

The OracleLib calls out to a chainlink aggregator receiving the latestRoundData(). It then checks freshness by verifying that it is not more than 3 hours old (TIMEOUT). This check is insufficient.

Vulnerability Details

If there is a problem with chainlink starting a new round and finding consensus on the new value for the oracle (e.g. chainlink nodes abandon the oracle, chain congestion, vulnerability/attacks on the chainlink system) consumers of this contract may continue using outdated stale data (if oracles are unable to submit no new round is started).
Reference: https://consensys.io/diligence/audits/2021/09/fei-protocol-v2-phase-1/#chainlinkoraclewrapper---latestrounddata-might-return-stale-results

Impact

By design, if a price is stale, the function ought to revert, and render the DSCEngine unusable (https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/libraries/OracleLib.sol#L11).
This is not achieved in completeness and hence putting the protocol & funds at risk.

Tools Used

Manual verification.

Recommendations

Recommend adding the following checks:

(uint80 roundId, int256 answer, uint256 startedAt, uint256 updatedAt, uint80 answeredInRound) =
priceFeed.latestRoundData();
//@audit add these 3 lines of code
require(answer > 0, "Chainlink price <= 0");
require(updatedAt != 0, "Incomplete round");
require(answeredInRound >= roundId, "Stale price");

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