Cryptocurrency hacks have become increasingly common, yet instances where attackers take substantial risks only to gain minimal rewards are rare. Such an unusual scenario unfolded recently. An attacker discovered a vulnerability in Hyperbridge's cross-chain gateway, which enables the transfer of assets between different blockchain networks. The attacker exploited this weakness to mint 1 billion Polkadot tokens, valued at approximately $1.19 billion, on the Ethereum network and subsequently sold them for around $237,000 in ether.
This incident highlights the ongoing issue of bridge vulnerabilities in 2026, following a $270 million exploit on Solana's Drift Protocol last month. The attack targeted Hyperbridge's EthereumHost contract, specifically the mechanism by which it validates incoming cross-chain messages before passing them to the TokenGateway. Bridges, which facilitate the movement of coins between blockchain networks, remain a weak point in cross-chain architecture due to their administrative control over token contracts on destination chains. This means a single validation failure can grant an attacker unlimited token minting capabilities.
The attack began when the perpetrator submitted a forged message via dispatchIncoming, which was then routed to TokenGateway.onAccept. However, 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 suggests 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 then 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 routed them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting roughly 108.2 ETH across multiple swaps at varying prices. The limited liquidity in the bridged DOT pool on Ethereum worked against the attacker, capping their potential profit. Typically, weak liquidity is a significant issue for large traders, but in this instance, it prevented the attacker from realizing the full value of the minted tokens. The bridged DOT pool's limited depth meant that the 1 billion tokens overwhelmed 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 greater. 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 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.