While cryptocurrency hacks are not uncommon, it's rare for attackers to take significant risks and end up with relatively minor gains. This unusual scenario unfolded on Sunday when an attacker exploited a vulnerability in Hyperbridge's cross-chain gateway, which connects different blockchains, resulting in the minting of 1 billion Polkadot tokens, valued at $1.19 billion, on Ethereum. The attacker then sold these tokens for approximately $237,000 worth of ether.
This incident is the latest in a series of bridge vulnerabilities in 2026, including a $270 million Drift Protocol exploit on Solana last month. The vulnerability in this case was found in how Hyperbridge's EthereumHost contract validates incoming cross-chain messages before passing them to the TokenGateway, rather than in Polkadot's core network, which remained unaffected.
Bridges are particularly vulnerable as they hold administrative control over token contracts on destination chains, meaning a single validation failure can grant an attacker unlimited minting capabilities. The attack began when the attacker 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, suggesting that proof validation was either absent or circumventable for this specific call path.
This allowed 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 this 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 roughly 108.2 ETH across multiple swaps at slightly different prices. The lack of liquidity in the market worked against the attacker, limiting their profit.
The bridged DOT pool on Ethereum had limited depth, meaning the 1 billion tokens overwhelmed the available liquidity, resulting in the attacker receiving only a fraction of a cent per token. If this 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 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.