Cryptocurrency hacks have become commonplace, but instances where attackers take significant risks only to gain minimal rewards are rare. Such a scenario unfolded recently.
An attacker exploited a flaw in Hyperbridge's cross-chain gateway, which connects various blockchains, resulting in the minting of 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network. These tokens were subsequently sold for around $237,000 worth of ether.
This exploit is the latest in a series of bridge vulnerabilities that have been discovered in 2026, including a $270 million drain on Solana's Drift Protocol last month. The targeted bridge contract, rather than Polkadot's core network, was the vulnerable point in this attack. The native DOT token remained unaffected. The vulnerability lay in 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, continue to be 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 with the submission of 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, instead storing an all-zeros commitment value. This suggested that the proof validation was either absent or circumventable for this specific call path, 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 routed them through Odos Router V3 into a Uniswap V4 DOT-ETH pool. This resulted in the extraction of roughly 108.2 ETH across multiple swaps at slightly different prices. However, the attacker's profit was capped due to weak liquidity in the market. The bridged DOT pool on Ethereum had limited depth, meaning the 1 billion tokens overwhelmed the available liquidity, resulting in the attacker receiving only a fraction of a cent per token.
On a deeper pool or a higher-value bridged asset, the same vulnerability would have led to significantly larger losses. As of Monday morning, DOT was trading just under $1.20.
The exploit was flagged by CertiK, which confirmed the attack vector as the Hyperbridge gateway contract and estimated the attacker's profit to be around $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.