MyCut

AI First Flight #8
Beginner FriendlyFoundry
EXP
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Submission Details
Severity: high
Valid

closePot() divides by all players but only pays claimants, permanently locking the majority of remaining funds

Root + Impact

Description

The closePot() function computes the per-claimant bonus by dividing the distributable remainder by i_players.length (the total number of registered players). However, the payment loop only iterates over claimants — the subset of players who called claimCut() within 90 days. The difference between what was divided and what was paid is permanently stuck in the Pot contract, which has no sweep or rescue function.

// Pot.sol :: closePot()
uint256 managerCut = remainingRewards / managerCutPercent;
i_token.transfer(msg.sender, managerCut);
// @> Division uses ALL registered players as denominator
uint256 claimantCut = (remainingRewards - managerCut) / i_players.length;
// @> Loop only pays the smaller claimants subset
for (uint256 i = 0; i < claimants.length; i++) {
_transferReward(claimants[i], claimantCut);
}
// @> (i_players.length - claimants.length) * claimantCut is never sent

Risk

Likelihood:

  • The denominator mismatch is unconditional — any time claimants.length < i_players.length (i.e. at least one player did not claim), funds are locked.

  • In practice, contests routinely have non-claiming participants (disqualified players, lost keys, missed deadlines), so this triggers in virtually every real contest.

Impact:

  • The locked amount scales with both the number of non-claimants and the size of the remaining pool — potentially locking the majority of all deposited funds.

  • Funds are unrecoverable: Pot has no owner rescue, no fallback, and no further distribution path after closePot() completes.

Proof of Concept

// 4 players registered, only 1 claims in time
// remainingRewards at close = 1000e18
uint256 managerCut = 1000e18 / 10; // = 100e18
uint256 claimantCut = (1000e18 - 100e18) / 4; // = 225e18 ← divided by 4
// Loop pays only claimants.length = 1 address
// Paid out : 225e18
// Locked : 900e18 - 225e18 = 675e18 ← 67.5% of remaining pool

Recommended Mitigation

uint256 claimantCut = (remainingRewards - managerCut)
- / i_players.length;
+ / claimants.length; // divide only by those who actually claimed
+ // Guard: if nobody claimed, send everything to the manager
+ if (claimants.length == 0) {
+ i_token.safeTransfer(msg.sender, remainingRewards);
+ return;
+ }
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge 2 days ago
Submission Judgement Published
Validated
Assigned finding tags:

[H-02] Incorrect logic in `Pot::closePot` leads to unfair distribution to `claimants`, potentially locking the funds with no way to take that out

## Description in `closePot` function while calclulating the shares for claimaint cut, `i_players.length` is used, instead of `claimants.length`, causing low amount being distributed to claimants. ## Vulnerability Details [2024-08-MyCut/src/Pot.sol at main · Cyfrin/2024-08-MyCut (github.com)](https://github.com/Cyfrin/2024-08-MyCut/blob/main/src/Pot.sol#L57) `Pot::closePot` function is meant to be called once contest passed 90 days, it sends the owner cut to owner and rest is splitted among the users who claimed b/w 90 days period. However, current implementation is wrong.&#x20; It uses total users (i_players.length) instead of the users (claimants.length) who claimed during the duration. This creates an unfair distribution to the participants and some of the funds could be locked in the contract. In worst case scenerio, it could be 90% if nobody has claimed from the protocol during the 90 days duration. ## POC In existing test suite, add following test: ```solidity function testUnfairDistributionInClosePot() public mintAndApproveTokens { // Setup address[] memory testPlayers = new address[](3); testPlayers[0] = makeAddr("player1"); testPlayers[1] = makeAddr("player2"); testPlayers[2] = makeAddr("player3"); uint256[] memory testRewards = new uint256[](3); testRewards[0] = 400; testRewards[1] = 300; testRewards[2] = 300; uint256 testTotalRewards = 1000; // Create and fund the contest vm.startPrank(user); address testContest = ContestManager(conMan).createContest( testPlayers, testRewards, IERC20(ERC20Mock(weth)), testTotalRewards ); ContestManager(conMan).fundContest(0); vm.stopPrank(); // Only player1 claims their reward vm.prank(testPlayers[0]); Pot(testContest).claimCut(); // Fast forward 91 days vm.warp(block.timestamp + 91 days); // Record balances before closing the pot uint256 player1BalanceBefore = ERC20Mock(weth).balanceOf( testPlayers[0] ); // Close the contest vm.prank(user); ContestManager(conMan).closeContest(testContest); // Check balances after closing the pot uint256 player1BalanceAfter = ERC20Mock(weth).balanceOf(testPlayers[0]); // Calculate expected distributions uint256 remainingRewards = 600; // 300 + 300 unclaimed rewards uint256 ownerCut = remainingRewards / 10; // 10% of remaining rewards uint256 distributionPerPlayer = (remainingRewards - ownerCut) / 1; // as only 1 user claimed uint256 fundStucked = ERC20Mock(weth).balanceOf(address(testContest)); // actual results console.log("expected reward:", distributionPerPlayer); console.log( "actual reward:", player1BalanceAfter - player1BalanceBefore ); console.log("Fund stucked:", fundStucked); } ``` then run `forge test --mt testUnfairDistributionInClosePot -vv` in the terminal and it will show following output: ```js [⠊] Compiling... [⠒] Compiling 1 files with Solc 0.8.20 [⠘] Solc 0.8.20 finished in 1.63s Compiler run successful! Ran 1 test for test/TestMyCut.t.sol:TestMyCut [PASS] testUnfairDistributionInClosePot() (gas: 905951) Logs: User Address: 0x6CA6d1e2D5347Bfab1d91e883F1915560e09129D Contest Manager Address 1: 0x7BD1119CEC127eeCDBa5DCA7d1Bd59986f6d7353 Minting tokens to: 0x6CA6d1e2D5347Bfab1d91e883F1915560e09129D Approved tokens to: 0x7BD1119CEC127eeCDBa5DCA7d1Bd59986f6d7353 expected reward: 540 actual reward: 180 Fund stucked: 360 Suite result: ok. 1 passed; 0 failed; 0 skipped; finished in 1.58ms (506.33µs CPU time) ``` ## Impact Loss of funds, Unfair distribution b/w users ## Recommendations Fix the functions as shown below: ```diff function closePot() external onlyOwner { if (block.timestamp - i_deployedAt < 90 days) { revert Pot__StillOpenForClaim(); } if (remainingRewards > 0) { uint256 managerCut = remainingRewards / managerCutPercent; i_token.transfer(msg.sender, managerCut); - uint256 claimantCut = (remainingRewards - managerCut) / i_players.length; + uint256 totalClaimants = claimants.length; + if(totalClaimant == 0){ + _transferReward(msg.sender, remainingRewards - managerCut); + } else { + uint256 claimantCut = (remainingRewards - managerCut) / claimants.length; for (uint256 i = 0; i < claimants.length; i++) { _transferReward(claimants[i], claimantCut); } } + } } ```

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