MyCut
AI First Flight #8
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Submission Details
Severity: high
Valid

`closePot` divides the leftover reward pool by the total player count instead of the claimant count, permanently locking unclaimed rewards

nahmstay

Root + Impact

Description

  • After the 90-day claim window closes, closePot is meant to take the manager's 10% cut and split the remaining unclaimed pool equally among the players who claimed in time (the claimants), fully emptying the Pot.

  • closePot instead sizes each claimant's share by dividing the leftover by i_players.length (every registered player) while the payout loop only pays the claimants subset. Because a leftover exists precisely when some players did not claim, the divisor is always larger than the number of recipients, so the pool is under-distributed and the remainder is stranded forever — the Pot has no rescue function.

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; // divisor should be claimants.length
for (uint256 i = 0; i < claimants.length; i++) {
_transferReward(claimants[i], claimantCut);
}
}
}

Risk

Likelihood:

  • When at least one registered player does not claim within the 90-day window — the exact condition that leaves remainingRewards > 0 — and the manager calls closeContest.

  • When the player roster is large relative to the remaining pool, claimantCut truncates to 0 and the entire leftover (minus the manager's 10%) is locked.

Impact:

  • A portion of every partially-claimed contest's leftover — scaling toward ~100% as the roster grows relative to the pool — is permanently locked in the Pot with no recovery path.

  • The in-time claimants receive strictly less than the redistribution the protocol guarantees them.

Proof of Concept

Two players owed 50 each; only player1 claims; at close 23 of the 50-token leftover are stranded. Verified as a unit test (test/PoC_ClosePotLockedFunds.t.sol) and as a 10,000-run conservation fuzz test (test/PoC_FuzzConservation.t.sol).

function testLeftoverPermanentlyLockedByWrongDenominator() public {
// Fund a 2-player pot (50 + 50 = 100).
vm.startPrank(user);
contest = ContestManager(conMan).createContest(players, rewards, IERC20(weth), totalRewards);
ContestManager(conMan).fundContest(0);
vm.stopPrank();
​
// Only player1 claims; player2 is a no-show. remainingRewards = 50, claimants = [player1].
vm.prank(player1);
Pot(contest).claimCut();
​
// Manager closes after 90 days.
vm.warp(block.timestamp + 91 days);
vm.prank(user);
ContestManager(conMan).closeContest(contest);
​
// managerCut = 5, claimantCut = (50-5)/2 = 22, distributed = 27, stranded = 23.
// Reverts with 23 on buggy code; passes (0) once the divisor is claimants.length.
assertEq(weth.balanceOf(contest), 0, "leftover must be fully distributed, none locked");
}

Recommended Mitigation

- uint256 claimantCut = (remainingRewards - managerCut) / i_players.length;
- for (uint256 i = 0; i < claimants.length; i++) {
- _transferReward(claimants[i], claimantCut);
- }
+ if (claimants.length > 0) {
+ uint256 claimantCut = (remainingRewards - managerCut) / claimants.length;
+ for (uint256 i = 0; i < claimants.length; i++) {
+ _transferReward(claimants[i], claimantCut);
+ }
+ }
+ remainingRewards = 0; // finalize: also prevents re-distribution on a second closePot
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge about 6 hours 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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