Cryptocurrency hacks have become commonplace, but instances where attackers take substantial risks only to reap minimal rewards are rare. One such incident occurred on Sunday, where an attacker exploited a weakness in the Hyperbridge cross-chain gateway, connecting various blockchains, to mint 1 billion Polkadot tokens valued at $1.19 billion on the Ethereum network and subsequently sold them for approximately $237,000 in ether. This exploit contributes to the growing list of vulnerabilities found in bridge protocols in 2026, including the $270 million Drift Protocol incident on Solana last month.
The attack targeted the bridge contract rather than Polkadot's core network, leaving the native DOT token unaffected. The vulnerability was rooted 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 different 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 validation failures that can grant attackers 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 failed to verify the message against a valid cross-chain state commitment from Polkadot, instead storing an all-zeros commitment value. This allowed the gateway to process the message as legitimate, transferring admin rights to the attacker's address. With admin control, the attacker minted 1 billion tokens and routed them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting roughly 108.2 ETH across multiple swaps.
However, the limited liquidity of the bridged DOT pool on Ethereum worked against the attacker, capping their profit. The pool's shallow depth meant that the 1 billion tokens overwhelmed the available liquidity, resulting in the attacker receiving only a fraction of a cent per token. This incident highlights the importance of robust validation mechanisms in cross-chain architecture to prevent such exploits.
CertiK identified the exploit, confirming that the attack vector was the Hyperbridge gateway contract, and the attacker profited 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 similar attacks.