contracts-governance-attack

DAO Governance Attack

Attack classes

1. Flash-loan-backed vote

DAOs that grant voting power = current token balance (not snapshot of past balance) are vulnerable:

// Attack: borrow governance token, vote, return loan, all in one tx
function attack() external {
    // 1. Flash-borrow gov tokens
    IFlashLoan(aave).flashLoan(address(this), govToken, 1_000_000e18, "");
}
function executeOperation(...) external {
    // 2. Vote on the malicious proposal
    governor.castVote(proposalId, 1);   // 1 = for
    // 3. Repay loan + premium (automatic by flash-loan callback)
}

This is what happened to Beanstalk (April 2022, $182M loss) — attacker flash-borrowed Beanstalk gov tokens, voted to drain the treasury, repaid the loan. Same block.

Defense check: Does getVotes(address, blockNumber) reference a past snapshot? If yes (Compound's GovernorBravo pattern, OZ Governor with ERC20Votes + getPastVotes), flash-loan vote doesn't work.

2. Delegation hijack

ERC20Votes lets users delegate. If a contract holds gov tokens and delegates to itself, controlling that contract = controlling the votes.

// If the target DAO has a contract holding tokens that delegates to itself,
// and that contract is upgradeable/has an admin function:
upgradeableContract.upgradeAndCall(newImpl, abi.encodeWithSelector(redelegate.selector, attacker));
// Now attacker controls those votes.

3. Quorum dilution attack

If quorum = % of total supply (not % of currently-active voters), an attacker can mint or stake extra tokens to push quorum out of reach:

// Some DAOs base quorum on totalSupply()
// Attacker mints a bunch of tokens to themselves (via legit minting if they're holder)
// Quorum requirement now too high for real voters to meet → all proposals fail

4. Proposal spam DoS

GovernorBravo has a proposalThreshold. If low, attacker spams proposals to:

• Burn proposers' gas
• Confuse the UI
• Push real proposals out of the active window