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code-423n4 / 2021-06-pooltogether-findings

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Overly permissive threshold check allows high yield loss #69

Open code423n4 opened 3 years ago

code423n4 commented 3 years ago

Handle

0xRajeev

Vulnerability details

Impact

The Yearn yield source defines maxLosses as: “Max % of losses that the Yield Source will accept from the Vault in BPS” and uses a setter setMaxLosses() to allow owner to set this value. However, the threshold check implemented only checks if this value is less than 10_000 or 100%, which is a good sanity check but allows loss of even 100%. The buffer for the loss is to avoid funds being locked in the Yearn vault in any emergency situation.

Impact: If the losses are really high for some reason, it will impact the interest and the prizes.

Proof of Concept

https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/yield-source/YearnV2YieldSource.sol#L28-L29

https://github.com/code-423n4/2021-06-pooltogether/blob/85f8d044e7e46b7a3c64465dcd5dffa9d70e4a3e/contracts/yield-source/YearnV2YieldSource.sol#L96

Tools Used

Manual Analysis

Recommended Mitigation Steps

Perform a tighter upper threshold check to allow a more acceptable max loss value in setMaxLosses()

asselstine commented 3 years ago

Yield sources are controlled by governance, so this isn't a concern