Cryptocurrency hacks have become commonplace, but instances where attackers take significant risks only to gain minimal rewards are rare. Such a scenario occurred on Sunday when an attacker exploited a vulnerability in the Hyperbridge cross-chain gateway, which connects various blockchains. The attacker successfully minted 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network and sold them for roughly $237,000 worth of ether. This incident is the latest in a string of bridge vulnerabilities that have been exposed in 2026, including a $270 million Drift Protocol breach on Solana last month.
The attack did not target Polkadot's core network, and its native token, DOT, remained unaffected. Instead, the vulnerability was found in the Hyperbridge EthereumHost contract, which is responsible for validating incoming cross-chain messages before passing them to the TokenGateway.
Bridges, designed to facilitate the transfer of coins between different blockchains, are often the weakest link in cross-chain architecture. This is because they hold admin-level control over token contracts on destination chains, making them a prime target for attackers. A single validation failure can grant an attacker the ability to mint an unlimited supply of tokens. The attack unfolded when the attacker submitted a forged message via dispatchIncoming, which was then routed to TokenGateway.onAccept.
However, 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. As a result, the accepted message executed changeAdmin on the bridged Polkadot token contract, 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. The limited liquidity in the bridged DOT pool on Ethereum worked against the attacker, capping their profit. The pool's weak depth meant that the 1 billion tokens overwhelmed the available liquidity, resulting in the attacker receiving only a fraction of a cent per token. If the vulnerability had been exploited on a deeper pool or a higher-value bridged asset, the losses would have been significantly larger.
The value of DOT stood at just under $1.20 during Asian morning hours on Monday. CertiK identified the exploit and confirmed that the attack vector was the Hyperbridge gateway contract, with the attacker profiting around $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.