Cryptocurrency hacks have become all too common, but instances where attackers take significant risks only to gain minimal rewards are rare. One such instance occurred on Sunday, where an attacker exploited a vulnerability in the Hyperbridge cross-chain gateway, connecting various blockchains, and minted 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network.
The attacker then sold these tokens for roughly $237,000 in ether. This exploit is the latest in a series of bridge vulnerabilities that have been uncovered in 2026, including a $270 million Drift Protocol exploit on Solana last month. The attack targeted the bridge contract rather than Polkadot's core network, with the native DOT token remaining unaffected.
The vulnerability lay in the way 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 unlimited supply. 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 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 approximately 108.2 ETH across multiple swaps. The limited liquidity of 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 with a higher-value bridged asset, the same vulnerability would have resulted in significantly larger losses.
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 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.