Cryptocurrency hacks have become all too common, but it's rare for attackers to take such huge risks only to end up with relatively modest gains. This unusual scenario unfolded on a recent Sunday. An attacker discovered a vulnerability in the Hyperbridge cross-chain gateway, which connects various blockchains, and exploited it to mint 1 billion Polkadot tokens on the Ethereum network, valued at $1.19 billion. However, due to the low liquidity of the bridged DOT token, the attacker was only able to sell them for around $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 exploit on Solana's Drift Protocol last month. The attack on Sunday targeted the bridge contract, rather than Polkadot's core network, and the native DOT token remained unaffected.
The vulnerability lay in the way Hyperbridge's EthereumHost contract validated incoming cross-chain messages before passing them to the TokenGateway. Bridges, which facilitate the transfer of coins between different blockchains, are often the weakest link in cross-chain architecture because they hold administrative control over token contracts on destination chains. This means that a single validation failure can grant an attacker unlimited access to mint tokens.
The attack began when the perpetrator submitted a forged message via dispatchIncoming, which was then routed to TokenGateway.onAccept. However, the request receipts check, which should have verified the message against a valid cross-chain state commitment from Polkadot, failed to do so, allowing the gateway to process the message as legitimate. The accepted message then executed changeAdmin on the bridged Polkadot token contract, transferring administrative rights to the attacker's address. With administrative 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 around 108.2 ETH across multiple swaps at slightly different prices.
The limited liquidity of the bridged DOT pool on Ethereum worked against the attacker, capping their profits. If the same vulnerability had been exploited on a deeper pool or a higher-value bridged asset, the losses would have been significantly larger. As of Monday morning, DOT was trading just under $1.20.
The exploit was flagged by CertiK, which confirmed that the attack vector was the Hyperbridge gateway contract and that the attacker had 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 the same forged-message attack vector.