While cryptocurrency hacks are becoming increasingly common, it's rare for attackers to take significant risks only to walk away with relatively modest gains. However, this unusual scenario played out recently. An attacker successfully exploited a vulnerability in the Hyperbridge cross-chain gateway, which connects various blockchains, and minted 1 billion Polkadot tokens on the Ethereum network, valued at approximately $1.19 billion. The attacker then sold these tokens for around $237,000 in ether.
This incident highlights the growing concern of bridge vulnerabilities in 2026, following a $270 million drain on the Drift Protocol on Solana last month. The recent exploit targeted the bridge contract rather than Polkadot's core network, and the native DOT token remained unaffected. The issue stemmed from how Hyperbridge's EthereumHost contract validated incoming cross-chain messages before passing them to the TokenGateway. Bridges, which facilitate the transfer of coins between blockchains, are often the weakest 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 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, 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, the limited liquidity in the bridged DOT pool on Ethereum worked against the attacker, capping their profit.
The pool's limited 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. According to reports, DOT was trading just under $1.20 during Asian morning hours on Monday.
The incident was flagged by CertiK, which confirmed that the attack vector was the Hyperbridge gateway contract and that 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 the same attack vector.