First Flight #17: Dussehra
First Flight #17
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Submission Details
Severity: low
Invalid

Reentrancy Attack Vulnerability in withdraw Function Due to Missing Check-Effects-Interactions

mujahideth

Summary

The withdraw function in the Dussehra contract is susceptible to reentrancy attacks due to the incorrect implementation of the check-effects-interactions pattern. This allows an attacker to recursively call the withdraw function and drain the contract's funds.

Vulnerability Details

The withdraw function in the Dussehra contract does not follow the check-effects-interactions pattern, which leaves it vulnerable to reentrancy attacks. This function allows the selected Ram to withdraw funds, but because the state variable totalAmountGivenToRam is updated after the external call to msg.sender.call{value: amount}(""), an attacker can exploit this by recursively calling the withdraw function before totalAmountGivenToRam is set to 0.

Impact

Repeatedly call the withdraw function and withdraw the same funds multiple times.

Tools Used

Manual review

Recommendations

To mitigate this vulnerability, implement the check-effects-interactions pattern properly by updating the state before making any external calls.

function withdraw() public RamIsSelected OnlyRam RavanKilled {
if (totalAmountGivenToRam == 0) {
revert Dussehra__AlreadyClaimedAmount();
}
uint256 amount = totalAmountGivenToRam;
totalAmountGivenToRam = 0; // Update state before external call
(bool success, ) = msg.sender.call{value: amount}("");
require(success, "Failed to send money to Ram");
}
Updates

Lead Judging Commences

bube Lead Judge over 1 year ago
Submission Judgement Published
Invalidated
Reason: Non-acceptable severity
Assigned finding tags:

Invalid - reentrancy in withdraw

The `withdraw` function sends the given amount to Ram. If the attacker calls the `withdraw` function again before the state variable is changed, the function will revert because there are no more funds in the contract. This reentrancy has no impact for the protocol. It is recommended to follow the CEI pattern, but this is informational.

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