Nomad Bridge Hack

The Nomad Bridge hack stemmed from an extraordinarily simple yet devastating initialization error in a recent upgrade. During a routine upgrade, the Nomad team initialized the trusted root with the value 0x00 instead of the intended valid merkle root. This seemingly small error had catastrophic consequences.

The vulnerability effectively allowed any message to be automatically proven valid:

// Simplified representation of the vulnerable function
function process(bytes memory message, bytes32[] memory proof) public {
    bytes32 committedRoot = committedRoots[msg.sender];
    
    // The fatal bug: committedRoot was initialized to 0x00
    // Any message could be proven valid because the check below
    // would always pass when using 0x00 as proof
    if (MerkleLib.verify(committedRoot, proof, keccak256(message))) {
        // Process message and transfer funds
        _processMessage(message);
    }
}

The simplicity of the exploit meant that:

1. The initial attacker only needed to find a valid transaction on the bridge
2. They could then copy this transaction but change the recipient address to their own
3. Since the trusted root was 0x00, the transaction would be considered valid
4. They could withdraw funds they never deposited

Once the vulnerability was discovered, hundreds of users with varying levels of technical knowledge began copying the exploit pattern, leading to the mass extraction of funds from the bridge.