While cryptocurrency hacks are not uncommon, instances where attackers take significant risks only to gain minimal rewards are rare. Such a scenario unfolded on Sunday when an attacker exploited a vulnerability in Hyperbridge's cross-chain gateway, which connects various blockchains, to mint 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network. The attacker then sold these tokens for around $237,000 worth of ether.
This exploit highlights the ongoing issue of bridge vulnerabilities in 2026, following a $270 million drain on Solana's Drift Protocol last month and a social engineering attack that compromised infrastructure. The Sunday attack targeted Hyperbridge's EthereumHost contract, specifically the mechanism for validating incoming cross-chain messages before they are passed to the TokenGateway, rather than Polkadot's core network. As a result, Polkadot's native token, DOT, was not affected. Bridges, which facilitate the transfer of coins between different blockchains, remain a weak point in cross-chain architecture because they hold administrative 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 then routed to TokenGateway.onAccept.
However, the request receipts check, intended to verify the message against a valid cross-chain state commitment from Polkadot, contained an all-zeros commitment value, suggesting that proof validation was either missing or could be circumvented for this specific call path. Consequently, the gateway processed the message as legitimate.
The accepted message executed changeAdmin on the bridged Polkadot token contract, transferring administrative rights to the attacker's address. With administrative control, the attacker minted 1 billion tokens in a single transaction and transferred them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting approximately 108.2 ETH across multiple swaps at slightly different prices. The limited liquidity of the bridged DOT pool on Ethereum worked against the attacker, as 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 with a higher-value bridged asset, the same vulnerability could 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 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.