Cryptocurrency hacks are a common occurrence, but instances where attackers take significant risks and end up with minimal gains are rare. Such a scenario unfolded on Sunday when an attacker exploited a vulnerability in Hyperbridge's cross-chain gateway, which connects different blockchains, and minted 1 billion Polkadot tokens on Ethereum, valued at $1.19 billion, but only managed to sell them for around $237,000 worth of ether.
This exploit highlights the growing list of bridge vulnerabilities in 2026, including a $270 million Drift Protocol breach on Solana last month. The attack targeted the bridge contract, not Polkadot's core network, and the native DOT token remained unaffected.
The vulnerability was found in how Hyperbridge's EthereumHost contract validates 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 unlimited supply. The attack began when the attacker submitted 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 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 around 108.2 ETH across multiple swaps. However, the limited liquidity in the bridged DOT pool on Ethereum worked against the attacker, capping their profit. The attacker received only a fraction of a cent per token due to the pool's limited depth.
On a deeper pool or a higher-value bridged asset, the same vulnerability could have resulted in significantly larger losses. The price of DOT was just under $1.20 as of Monday morning. CertiK identified the exploit, confirming 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 not publicly commented on the exploit or disclosed whether other bridged token contracts using the same gateway are vulnerable to the same forged-message attack vector.