Yield-Convex contest - defsec's results

Handle

defsec

Vulnerability details

Impact

The _peek function in the contract Cvx3CrvOracle.sol fetches the asset price from a Chainlink aggregator using the latestRoundData function. However, there are no checks on timestamp, resulting in stale prices. The oracle wrapper calls out to a chainlink oracle receiving the latestRoundData(). It then checks freshness by verifying that the answer is indeed for the last known round.

Stale prices could put funds at risk. According to Chainlink's documentation, This function does not error if no answer has been reached but returns 0, causing an incorrect price fed to the PriceOracle. The external Chainlink oracle, which provides index price information to the system, introduces risk inherent to any dependency on third-party data sources. For example, the oracle could fall behind or otherwise fail to be maintained, resulting in outdated data being fed to the index price calculations of the AMM. Oracle reliance has historically resulted in crippled on-chain systems, and complications that lead to these outcomes can arise from things as simple as network congestion.

Proof of Concept

1. Navigate to the following contract.

"https://github.com/code-423n4/2022-01-yield/blob/main/contracts/Cvx3CrvOracle.sol#L120"

Tools Used

Recommended Mitigation Steps

Consider to add checks on the return data (Timestamp) with proper revert messages if the price is stale in the timestamp, for example:

(uint80 roundID, int256 price, , uint256 timeStamp, uint80 answeredInRound) = ETH_CHAINLINK.latestRoundData();
require(price > 0, "Chainlink price <= 0");
require(answeredInRound >= roundID, "...");
require(timeStamp != 0, "...");