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Submission Details
Severity: low
Invalid

ChainLinkOracle.sol Constructor Assumes Chainlink Price Feed Decimals Are Always ≤18

pelz

Summary

The ChainlinkOracle constructor incorrectly assumes that all Chainlink price feeds return decimals ≤ 18. This assumption can lead to underflow errors and miscalculations when Chainlink introduces price feeds with decimals greater than 18.

Vulnerability Details

Issue

The contract's constructor includes the following code:

constructor(address _chainlinkFeed) {
require(_chainlinkFeed != address(0), "INVADDR"); // Invalid address provided
priceFeed = AggregatorV3Interface(_chainlinkFeed);
// Chainlink oracles have ≤ 18 decimals, cannot underflow
normalizationFactor = 18 - priceFeed.decimals(); // @audit-issue: Assumes decimals are ≤ 18
}

The normalizationFactor calculation assumes that priceFeed.decimals() will always return a value ≤ 18. However, this is not guaranteed by the Chainlink protocol. Future price feeds might use decimals > 18, resulting in:

  • Underflow errors when calculating normalizationFactor.

  • Incorrect normalized prices, causing significant financial discrepancies.

Proof of Concept

  1. Consider a hypothetical price feed with decimals() = 20.

  2. The constructor calculates normalizationFactor = 18 - 20 = -2.

Impact

If the token decimals is greater than 18 it would cause an overflow/underflow error

Tools Used

  • Manual review

Recommendations

Validate Decimal Values: Add a require statement to ensure priceFeed.decimals() does not exceed 18:

uint8 decimals = priceFeed.decimals();
require(decimals <= 18, "Decimals exceed 18");
normalizationFactor = 18 - decimals;
Updates

Lead Judging Commences

n0kto Lead Judge 10 months ago
Submission Judgement Published
Invalidated
Reason: Non-acceptable severity
Assigned finding tags:

Informational or Gas / Admin is trusted / Pool creation is trusted / User mistake / Suppositions

Please read the CodeHawks documentation to know which submissions are valid. If you disagree, provide a coded PoC and explain the real likelyhood and the detailed impact on the mainnet without any supposition (if, it could, etc) to prove your point.

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