While cryptocurrency hacks are a common occurrence, instances where attackers take substantial risks only to reap minimal rewards are rare. Such an incident occurred on Sunday, involving the exploitation of a vulnerability in the Hyperbridge cross-chain gateway that connects various blockchains.
The attacker successfully minted 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 bridge vulnerabilities in 2026, including the $270 million Drift Protocol incident on Solana last month. The attack targeted the bridge contract, leaving Polkadot's core network and its native token DOT 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, designed to facilitate the transfer of coins between blockchains, remain a weak link in cross-chain architecture due to their admin-level control over token contracts on destination chains. A single validation failure can grant an attacker the ability to mint an unlimited supply of tokens.
The attack unfolded with the submission of a forged message via dispatchIncoming, which was routed to TokenGateway.onAccept. The request receipts check failed to verify the message against a valid cross-chain state commitment from Polkadot, allowing the gateway to process the message as legitimate.
The accepted message executed a changeAdmin function on the bridged Polkadot token contract, transferring admin rights to the attacker's address. With admin control, the attacker minted 1 billion tokens and sold them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting roughly 108.2 ETH. However, limited liquidity in the bridged DOT pool on Ethereum restricted the attacker's 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. 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 traded just under $1.20. The exploit was flagged by CertiK, which confirmed the attack vector as the Hyperbridge gateway contract and estimated the attacker's profit at approximately $237,000 from minting and selling the bridged tokens.
Hyperbridge has not publicly commented on the exploit or disclosed whether other bridged token contracts using the same gateway are vulnerable to the same attack vector.