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Submission Details
Severity: high
Valid

variance will always revert.

bareli

Summary

variance will always revert as we are calculating :

@>>uint256 diff = data[i] - mean; and lets suppose

dataarray is [1,2,3,4,5,6] so mean is 21/6 is eual to 3. so we call variance function in this we are assigning

uint256 diff = data[i] - mean ,so for the first element my diff will be 1-3 equal to -2 but its a unit256 that will cause a revert.

this will cause a revert of stddev as its calling the variance function.

Vulnerability Details

function variance(uint256\[] memory data) internal pure returns (uint256 ans, uint256 mean) {
mean = avg(data);
uint256 sum = 0;
for (uint256 i = 0; i < data.length; i++) {
@>>uint256 diff = data\[i] - mean;
sum += diff \* diff;
}
ans = sum / data.length;
}
/// @notice Compute the standard deviation of the data.
/// @dev Computes variance, and takes the square root.
/// @param data The data to compute the standard deviation for.
function stddev(uint256[] memory data) internal pure returns (uint256 ans, uint256 mean) {
(uint256 _variance, uint256 _mean) = variance(data);
mean = _mean;
ans = sqrt(_variance);
}

Impact

this will cause a revert in both variance and stddev.

Tools Used

Recommendations

@>>int256 diff = data[i] - mean;

Updates

Lead Judging Commences

inallhonesty Lead Judge 12 months ago
Submission Judgement Published
Validated
Assigned finding tags:

Underflow in computing variance

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