Sigvex
EVMExploit4 min read

Governance Attack Exploit Generator

Sigvex exploit generator that validates DAO governance vulnerabilities by simulating flash loan vote acquisition, insufficient quorum scenarios, and timelock bypass.

evmaccess-controlflash-loanexploit-generator

Governance Attack Exploit Generator

Overview

The governance attack exploit generator validates findings from the governance-attacks detector by simulating scenarios where an attacker acquires governance tokens via flash loan within a single transaction, casts votes on a malicious proposal, and executes it before the snapshot lock mechanism (if any) can prevent participation.

The most prominent example is the Beanstalk DAO flash loan governance attack (April 2022, $182M). The attacker borrowed $1B in DAI/USDC/USDT via a major DeFi lending venue, converted them to Beanstalk governance tokens, voted in favor of a malicious proposal that transferred all protocol funds to the attacker’s address, executed immediately (no timelock), and repaid the flash loan — all within a single transaction.

Note: Exploit generation in Sigvex is for vulnerability validation purposes only.

Attack Scenario

  1. Setup: The attacker identifies a governance contract without a voting snapshot mechanism (votes are counted at proposal execution time, not at proposal creation).
  2. Flash loan acquisition: Within a single transaction, the attacker borrows a massive amount of the governance token. With 1_000_000_000 voting tokens, the attacker’s vote weight exceeds all other participants combined.
  3. Vote: The attacker calls castVote(proposalId, FOR). The contract records the flash-loan-inflated balance as the vote weight.
  4. Execute: If the proposal has no timelock (or a timelock that already expired), the attacker calls execute(proposalId). The malicious proposal runs — typically draining treasury funds or updating privileged parameters.
  5. Repay: The attacker repays the flash loan with a portion of extracted funds. Net profit is the total protocol treasury minus flash loan fees.

Additional governance vulnerability patterns detected:

  • Insufficient quorum: A proposal passes with only 1% participation if quorum is set too low.
  • Whale control: A single address holds >50% of voting power (no diversification requirement).
  • Proposal spam: Governance contracts without proposal fees or caps can be DoS’d by flooding with spam proposals.

Exploit Mechanics

The generator runs four execution scenarios against the governance contract bytecode:

Scenario Token balance (slot 0) Quorum (slot 2) Timelock (slot 3) Snapshot (slot 4)
1 — Normal voter 1,000 10% 48h Required
2 — Flash loan attack 1,000,000,000 10% 0 (no timelock) Not required
3 — Low quorum 1,000 1% 0 Not required
4 — Protected 1,000 10% 48h Required

Calldata targets castVote(uint256,uint8) (selector 0x56781388) followed by execute(uint256) (selector 0xa217fddf).

Critical findings are raised when:

  • Flash loan scenario succeeds but normal scenario would not meet quorum → flash loan governance attack confirmed (confidence 0.90)
  • Low quorum scenario succeeds → insufficient quorum protection (confidence 0.85)
  • Both normal and flash loan succeed immediately → no timelock detected (confidence 0.85)

The generator produces a full PoC demonstrating the Beanstalk-style attack pattern.

Remediation

Multiple defenses are required in combination:

// 1. Vote snapshot at proposal creation time (prevents flash loan voting)
mapping(uint256 => mapping(address => uint256)) public voteSnapshotBalances;

function propose(...) external {
    uint256 proposalId = ...;
    // Capture token balances at this block, not at execution time
    snapshotBlock[proposalId] = block.number;
    voteSnapshotBalances[proposalId][msg.sender] =
        token.getPastVotes(msg.sender, block.number);
}

// 2. Mandatory timelock (48+ hours between proposal and execution)
uint256 public constant MIN_TIMELOCK = 2 days;

// 3. Quorum requirement (10%+ of circulating supply)
uint256 public constant MIN_QUORUM_PERCENT = 10;

// 4. Proposal fee to prevent spam
uint256 public constant PROPOSAL_FEE = 100e18; // 100 tokens

OpenZeppelin’s Governor with GovernorVotes, GovernorTimelockControl, and GovernorSettings provides these protections out of the box.

References