Devve — settlement pays the claimed amount, not the ETH received

Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: 37615-incorrect-handling-of-investment-amounts-zokyo-none-devve-ma. Standalone Foundry PoC and full write-up: 37615-incorrect-handling-of-investment-amounts-zokyo-none-devve-ma_exp in the evm-hack-registry mirror.

Vulnerability classes: vuln/logic/missing-check · vuln/logic/state-update

Reproduction: a self-contained Foundry PoC that compiles and runs offline with only forge-std — no fork and no RPC. Trace: output.txt. PoC: test/37615-incorrect-handling-of-investment-amounts-zokyo-none-devve-ma_exp.sol.

Key info#

TL;DR#

investInProjects adds msg.value to investorInvestedAmountPerProjectInETH and never checks that it equals users.amount. settleProjectOwnerFunds sets _amountToWithdraw to users.amount and transfers that.

An investor sends 40 ETH with users.amount of 10 ETH. The real deposit stored is 40 ETH. The credit stored is 10 ETH. Settlement pays the project owner 10 ETH. The treasury still holds 30 ETH.

The control requires msg.value == users.amount and transfers investorInvestedAmountPerProjectInETH. The same 40 ETH is credited and paid. The treasury ends at 0.

run() does not warp. The 40 ETH is msg.value on the single call.

The vulnerable code#

function investInProjects(Whitelist memory users) external payable {
    // @> VULN: msg.value is not required to equal users.amount
    investorInvestedAmountPerProjectInETH[users.projectId][msg.sender] += msg.value;
    creditedAmount[users.projectId][msg.sender] = users.amount;
}

function settleProjectOwnerFunds(Whitelist memory users) external {
    uint256 _amountToWithdraw = users.amount;
    // @> VULN: pays users.amount, not investorInvestedAmountPerProjectInETH
    payable(users.userAddress).transfer(_amountToWithdraw);
}

The fee check uses projectTotalCollectedInETH, which was increased by the real 40 ETH, so a 10 ETH withdrawal passes. The comment on the transfer in the report says that value should be the invested ETH.

Root cause#

Two fields describe one investment and nothing forces them to be equal. The balance mapping follows the ETH that arrived. The payout follows the amount in the calldata. Settlement then moves the calldata amount.

Preconditions#

• users.amount is 10 ETH. msg.value is 40 ETH. platformFee is 0, so the fee does not hide the gap.
• The owner address is the userAddress on the whitelist passed to settlement.
• Settlement runs once.
• No timestamp change happens inside run().

Attack walkthrough#

1. The investor calls investInProjects with 40 ETH and amount 10 ETH.
2. investorInvestedAmountPerProjectInETH becomes 40 ETH. creditedAmount becomes 10 ETH.
3. settleProjectOwnerFunds sets _amountToWithdraw to 10 ETH and transfers it to the owner.
4. The owner holds 10 ETH. The treasury holds 30 ETH.

Control: amount is 40 ETH and msg.value is 40 ETH. The credit is 40 ETH. Settlement transfers the invested balance, 40 ETH. The treasury holds 0.

Diagrams#

Impact#

The investor paid 40 ETH and is credited 10 ETH. The owner is paid 10 ETH instead of 40 ETH. 30 ETH remains in the treasury.

Remediation#

Require msg.value == users.amount in investInProjects. In settleProjectOwnerFunds, transfer investorInvestedAmountPerProjectInETH for that investor, not users.amount.

Sources#

• AuditVault finding 37615
• Zokyo, Devve, 30 June 2024

Taxonomy#

• severity/high
• vuln/logic/missing-check
• vuln/logic/state-update

Sources & further analysis#

Reproductions & code

• Standalone PoC + full trace: 37615-incorrect-handling-of-investment-amounts-zokyo-none-devve-ma_exp (evm-hack-registry mirror).
• AuditVault finding: 37615-incorrect-handling-of-investment-amounts-zokyo-none-devve-ma.

Alerts & third-party analyses

• Web3Sec X hacked database: search.
• Rekt leaderboard: search.
• Solodit incident search: search.

These dashboards index community alerts tweets, post-mortems, and independent write-ups. Reach them through the protocol name above to cross-check this reproduction against other analyses.