Cryptocurrency hacks are a regular occurrence, but 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, connecting various blockchains, resulting in the minting of 1 billion Polkadot tokens, valued at $1.19 billion, on Ethereum. The attacker then sold these tokens for roughly $237,000 in ether. This incident adds to the growing list of bridge vulnerabilities in 2026, following a $270 million drain on Solana's Drift Protocol last month.
The Sunday exploit specifically targeted the bridge contract and not Polkadot's core network, with the native DOT token remaining unaffected. The vulnerability was found in how Hyperbridge's EthereumHost contract validates incoming cross-chain messages before passing them to the TokenGateway. Bridges, which facilitate the movement 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.
This means a single validation failure can grant an attacker the ability to mint an unlimited supply of tokens. The attack involved the submission of 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, indicating either the absence or circumvention of proof validation for this specific call path. As a result, the gateway processed the message as legitimate, leading to the execution of changeAdmin on the bridged Polkadot token contract.
This transferred admin rights to the attacker's address, allowing them to mint 1 billion tokens in a single transaction. The tokens were then routed through Odos Router V3 into a Uniswap V4 DOT-ETH pool, from which the attacker extracted approximately 108.2 ETH across multiple swaps at slightly different prices.
The limited liquidity in the bridged DOT pool on Ethereum worked against the attacker, capping their profit. Typically, weak liquidity is a major issue for large traders, but in this case, it prevented the attacker from gaining more substantial profits. 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 larger.
As of Monday morning, DOT was trading just under $1.20. CertiK identified the exploit, confirming that the attack vector was indeed 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 forged-message attack vector.