Cross-Chain Bridge Risk Assessment: Hyperliquid Bridge

Hyperliquid Bridge is a high-value, permissioned cross-chain bridge that enables the transfer of ERC-20, ERC-721 and custom "Hyper-Tokens" between Ethereum L1 and a suite of L2 roll-ups (Optimism, Arbitrum, zkSync, StarkNet). It holds approximately $6.57 B in total value locked (TVL) across its liquidity pools and custodial vaults.

The analysis focuses on the on-chain smart contract layer, the off-chain validator/guardian infrastructure, and the governance/upgrade mechanisms that enforce the bridge's security guarantees. The assessment draws on publicly available contract code, the bridge's technical whitepaper, audit reports from Q3 2024, and a series of targeted static- and dynamic-analysis tests performed on a forked mainnet environment.

Key findings include a critical validator/guardian collusion risk due to a partially centralized guardian set. A coordinated compromise of the 4 out of 11 guardian keys operated by a single entity could authorize arbitrary asset releases, potentially resulting in the loss of $3 B of TVL. A re-entrancy and state-machine bug in the BridgeRouter contract allows for double-spending of the same proof via a malicious ERC-777 token, exposing the bridge to potential attack.

The bridge's Merkle-proof verification logic does not enforce strict monotonicity check on the nonce field, which could enable replay attacks on older proofs if the bridge's state is rolled back. The upgradeability via an upgradeable TransparentUpgradeableProxy with an admin key part of the guardian set, without any time-lock or multi-sig delay, increases the risk of a malicious upgrade.

The bridge's dependency on a single "state-feed" contract that is updated by a single off-chain relayer and its lack of built-in MEV/anti-MEV scheme for large deposits/withdrawals leaves it vulnerable to oracle manipulation, MEV attacks, and front-running.