#41894 [SC-Critical] Incorrect calculation of deposited rewards yeet leads to Staker's not being able to get their staked amount back

Submitted on Mar 19th 2025 at 08:41:12 UTC by @Oxgritty for Audit Comp | Yeet

• Report ID: #41894

• Report Type: Smart Contract

• Report severity: Critical

• Target: https://github.com/immunefi-team/audit-comp-yeet/blob/main/src/StakeV2.sol

• Impacts:

  • Protocol insolvency

Description

Brief/Intro

• StakingV2::accumulatedDeptRewardsYeet is used to calculate the amount of accumulated rewards in yeet that are not distributed yet.

• The problem here is that, this function doesn't account for the fact that when a staker calls StakingV2::startUnstake to start unstaking, their balance is still in the contract but subtracted from the totalSupply, so StakingV2::accumulatedDeptRewardsYeet mistakes the unstake amount as undistributed rewards.

Vulnerability Details

• When the manager would want to distribute rewards through StakingV2::executeRewardDistributionYeet, he would first call the StakingV2::accumulatedDeptRewardsYeet to know the amount available for distribution. This function would return an amount which includes the unStakeAmount, which staker unstaked by calling StakingV2::startUnstake.

• When the manager will call StakingV2::executeRewardDistributionYeet, it will convert (undistributed rewards + unStakeAmount) into vaultShares, meaning when the staker would call StakingV2::unstake to get his unStakeAmount amount back, this contract won't have enough unStakeAmount of stakingToken and function will revert.

Impact Details

Stakers not being able to withdraw their staked amount as the contract will not have enough funds.

References

• When a staker calls StakingV2::startUnstake his unstake amount will be deducted from the totalSupply.
• This unstake amount is not deducted in StakingV2::accumulatedDeptRewardsYeet.

Proof of Concept

POC: (NOTE: StakingToken is YEET)

Step 0: Checking Current Balances

• totalSupply = 0

• stakingToken.balanceOf(address(this)) = 0

Step 1: Staking

1. Alice(a staker) calls StakingV2::stake to stake 100e18 Yeet.

2. Bob(another staker) calls StakingV2::stake to stake 50e18 Yeet.

Current Balances:

• totalSupply = 150e18

• stakingToken.balanceOf(address(this)) = 150e18

Step 2: Initiating Unstaking process

Alice initiates unstaking process by calling StakingV2::startUnstake where unStakeAmount=100e18

Current Balances:

• totalSupply = 50e18

• stakingToken.balanceOf(address(this)) = 150e18

Step 3: Manager checks amount of stakingToken available for distribution by calling StakingV2::accumulatedDeptRewardsYeet. This function will return 100e18(150e18 - 50e18).

Step 4: Manager calls StakingV2::executeRewardDistributionYeet to distribute yeet rewards.

Here the value of (stakingParams.amount0Max + swapData.inputAmount would be equal to 100e18). After the execution of this function, the contract would have 100e18 yeet worth of vault Shares and 50e18 Yeet.

Current Balance:

• totalSupply = 50e18

• stakingToken.balanceOf(address(this)) = 50e18

Step 5: Finalize unstaking and get unStakeAmount back

Alice calls StakingV2::unstake to get her unStakeAmount(100e18) back. This function will fail because StakingV2.sol has only 50e18 Yeet.