Cryptocurrency hacks have become commonplace, but instances where attackers take significant risks only to gain minimal rewards are rare. One such incident occurred on Sunday, where an attacker exploited a vulnerability in the Hyperbridge cross-chain gateway, connecting various blockchains, to mint 1 billion Polkadot tokens on Ethereum, valued at $1.19 billion, and subsequently sold them for roughly $237,000 in ether.
This exploit highlights the growing list of bridge vulnerabilities in 2026, following a $270 million Drift Protocol incident on Solana last month. The Sunday attack targeted the bridge contract, leaving Polkadot's core network and its native DOT token unaffected. The vulnerability was found in the validation process of incoming cross-chain messages by Hyperbridge's EthereumHost contract before passing them to the TokenGateway.
Bridges, which facilitate the transfer of coins between blockchains, remain a weak point in cross-chain architecture due to their admin-level control over token contracts on destination chains, making them susceptible to attacks where a single validation failure can grant an attacker unlimited supply. The attack unfolded when the attacker submitted a forged message via dispatchIncoming, which was then routed to TokenGateway.onAccept. The request receipts check, intended to verify the message against a valid cross-chain state commitment from Polkadot, contained an all-zeros commitment value, indicating either absent or circumventable proof validation for this specific call path.
Consequently, the gateway processed the message as legitimate, executing changeAdmin on the bridged Polkadot token contract and transferring admin rights to the attacker's address. With admin control, the attacker minted 1 billion tokens in a single transaction and sold them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting approximately 108.2 ETH across multiple swaps at varying prices. However, the attacker's profit was capped due to weak liquidity in the bridged DOT pool on Ethereum, which was overwhelmed by the 1 billion tokens, resulting in the attacker receiving only a fraction of a cent per token. On a deeper pool or with a higher-value bridged asset, the same vulnerability could have led to significantly larger losses.
As of Monday morning, DOT trades just under $1.20. The exploit was flagged by CertiK, confirming the attack vector as the Hyperbridge gateway contract, with the attacker profiting approximately $237,000 from minting and selling the bridged tokens. Hyperbridge has yet to publicly comment on the exploit or disclose whether other bridged token contracts using the same gateway are vulnerable to the same forged-message attack vector.