While cryptocurrency hacks are becoming increasingly common, it's rare for attackers to take significant risks and end up with relatively modest gains. However, that's exactly what happened on Sunday when an attacker exploited a vulnerability in the Hyperbridge cross-chain gateway, which connects different blockchain networks. The attacker was able to mint 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network and then sell them for approximately $237,000 worth of ether. This exploit highlights the ongoing issue of bridge vulnerabilities in 2026, following a $270 million Drift Protocol hack on Solana last month.
The attack targeted the bridge contract rather than Polkadot's core network, and the native DOT token was not affected. The vulnerability was found in the way Hyperbridge's EthereumHost contract validates incoming cross-chain messages before passing them to the TokenGateway. Bridges are often the weakest link in cross-chain architecture because they hold admin-level control over token contracts on destination chains, making them a prime target for attackers.
The attack began 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. The accepted message then executed a changeAdmin function on the bridged Polkadot token contract, transferring admin rights to the attacker's address.
With admin control, the attacker was able to mint 1 billion tokens in a single transaction and then sell them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting roughly 108.2 ETH across multiple swaps at slightly different prices. The limited liquidity in the market worked against the attacker, capping their profits. The bridged DOT pool on Ethereum had limited depth, meaning the 1 billion tokens overwhelmed the available liquidity, and the attacker received only a fraction of a cent per token.
If the attack had occurred on a deeper pool or a higher-value bridged asset, the losses would have been significantly larger. The attack 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 forged-message attack vector.