# #42725 \[SC-Critical] startUnstake() Reduces Total Supply, but StakingToken Balance in contract Remains Constant, Leading to Inflated accumulatedDeptRewardsYeet() **Submitted on Mar 25th 2025 at 13:46:17 UTC by @libro9595 for** [**Audit Comp | Yeet**](https://immunefi.com/audit-competition/audit-comp-yeet) * **Report ID:** #42725 * **Report Type:** Smart Contract * **Report severity:** Critical * **Target:** * **Impacts:** * Direct theft of any user funds, whether at-rest or in-motion, other than unclaimed yield ## Description ## Vulnerability Details * When a user starts `unstaking`, the `totalSupply` variable is reduced, but the actual balance of the staking token remains unchanged. * As a result, the calculation of `accumulatedDeptRewardsYeet()` becomes inflated compared to the actual amount. * This can lead to an significantly more rewards distribution in the `executeRewardDistributionYeet()` function . ## Impact Details * Assume an attacker stakes k amount of tokens in the protocol. * The protocol’s total supply is X, and the totalSupply of stake token in the vault (denoted as Y) are greater than k (X > k and Y > k). * When the attacker calls the `startUnstake()` function, their staked amount is deducted from the total supply. As a result, the total supply becomes X - k. * However, the actual balance of staking tokens in the contract remains Y, as the tokens are not physically withdrawn during the unstaking process. * Ideally, the balance of rewards should reflect Y - k to account for the pending unstake. However, since the balance remains Y, it artificially inflates the calculated rewards. * The function `accumulatedDeptRewardsYeet()` calculates rewards as: * Accumulated Rewards = Y - (X - k) * This results in an inflated reward amount. * When the manager calls `executeRewardDistributionYeet()`, the protocol uses this incorrect `accumulatedDeptRewardsYeet()` value to distribute rewards. * As a result, the attacker can claim significantly more rewards than they are entitled to, causing a substantial loss of funds from the protocol. * Additionally, because the attacker has initiated the unstake without claiming immediately, they can exploit the inflated reward calculation for an extended period, draining further funds. ## Recommendation: * Add a new variable `uint256 public pendingUnstake` to track the tokens in the unstaking process. Increment `pendingUnstake` in the startUnstake() function and decrement it when the `unstake` is completed.\ Update the `accumulatedDeptRewardsYeet()` function to subtract pendingUnstake from the calculation, ensuring rewards are ## Proof of Concept ## Proof of Concept * totoal suppy = x * total balance = y ### **Step 1: Staking Tokens** * The attacker deposits **k tokens** using the `stake()` function. * After this action: * Total supply of staked tokens becomes **X + k**. * Contract’s actual token balance becomes **Y + k**. * The attacker begins earning staking rewards. ### **Step 2: Earning Rewards** * The attacker waits to accumulate rewards. * The manager periodically calls `executeRewardDistribution()` to distribute rewards, increasing the `rewardIndex`. ### **Step 3: Initiating Unstake Without Actual Token Transfer** * The attacker calls `startUnstake(k)` to initiate the unstaking process before the executeRewardDistribution() . * The `totalSupply` is reduced by **k tokens** (“**totalSupply = X**”). * However, the actual token balance in the contract remains **Y + k**. * The staked tokens remain in the contract during the vesting period. ### **Step 4: Executing Reward Distribution** * The manager calls `executeRewardDistributionYeet()`. * The function uses `accumulatedDeptRewardsYeet()` to calculate rewards based on the following formula: ``` Accumulated Rewards = Y + k - X ``` * Since `totalSupply` (**X**) is now artificially reduced, the function falsely assumes excess rewards. * The inflated rewards are distributed to stakers, including the attacker. ### **Step 5: Claiming Excessive Rewards** * The attacker calls `claimRewardsInToken()` to withdraw rewards. * Due to the inflated reward calculation, the attacker claims a significantly higher amount of rewards than they are entitled to. * This results in a substantial loss of funds from the protocol. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. 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