Cryptocurrency hacks are a common occurrence, but instances where attackers take significant risks only to gain minimal rewards are rare. Such a scenario unfolded on a recent Sunday.
An attacker leveraged a vulnerability in Hyperbridge's cross-chain gateway, which connects multiple blockchains, to mint 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network, and subsequently sold them for roughly $237,000 in ether. This exploit highlights the growing list of bridge vulnerabilities in 2026, including a $270 million drain on Solana's Drift Protocol last month.
The attack targeted the bridge contract, not Polkadot's core network, with the native DOT token remaining unaffected. The vulnerability was found in the validation process of incoming cross-chain messages by Hyperbridge's EthereumHost contract before passing them to the TokenGateway.
Bridges, which facilitate the movement 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 involved submitting 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 transferred admin rights to the attacker's address, enabling them to mint 1 billion tokens and sell them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, resulting in approximately 108.2 ETH.
The limited liquidity in the bridged DOT pool on Ethereum worked against the attacker, capping their profit. If the vulnerability had been exploited on a deeper pool or a higher-value bridged asset, the losses would have been significantly larger. The attack vector was confirmed by CertiK, with the attacker profiting around $237,000 from the exploit.
Hyperbridge has yet to publicly comment on the incident or disclose whether other bridged token contracts using the same gateway are vulnerable to similar attacks.