While cryptocurrency hacks are not uncommon, instances where attackers take significant risks only to gain minimal rewards are rare. Such a scenario occurred on Sunday when an attacker exploited a weakness in the Hyperbridge cross-chain gateway, which connects various blockchains, resulting in the creation of 1 billion Polkadot tokens on Ethereum, valued at $1.19 billion, and selling them for approximately $237,000 in ether. This incident adds to 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 existed in the validation process of incoming cross-chain messages by Hyperbridge's EthereumHost contract before passing them to the TokenGateway. Bridges, which facilitate the transfer of coins between blockchains, remain the most vulnerable component in cross-chain architecture due to their administrative control over token contracts on destination chains.
A single validation failure can grant an attacker the ability to create an unlimited supply of tokens. The attack unfolded 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 a changeAdmin function on the bridged Polkadot token contract, transferring administrative rights to the attacker's address.
With administrative control, the attacker created 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 different prices. However, low liquidity in the market limited the attacker's profit.
The bridged DOT pool on Ethereum had limited depth, causing the 1 billion tokens to overwhelm 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.
As of Monday morning, DOT was trading just under $1.20. CertiK identified the exploit, confirming that the attack vector was the Hyperbridge gateway contract and the attacker profited around $237,000 from creating 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 attack vector.