Cryptocurrency hacks have become increasingly common, but it's rare for attackers to take significant risks and walk away with relatively minor gains. However, this unusual scenario played out recently. An attacker exploited a weakness in Hyperbridge's cross-chain gateway, which connects different blockchains, and minted 1 billion Polkadot tokens on Ethereum, valued at $1.19 billion, before selling them for around $237,000 worth of ether.
This incident is the latest in a series of bridge vulnerabilities that have been exposed in 2026, including a $270 million Drift Protocol breach on Solana last month. The attack targeted the bridge contract, rather than Polkadot's core network, and the native DOT token was unaffected. The vulnerability lay in how Hyperbridge's EthereumHost contract validated incoming cross-chain messages before passing them to the TokenGateway.
Bridges, which facilitate the transfer of coins between blockchains, remain a weak point in cross-chain architecture due to their admin-level control over token contracts on destination chains. This means that a single validation failure can grant an attacker unlimited supply. The attack unfolded when the attacker submitted a forged message via dispatchIncoming, which was 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 executed changeAdmin on the bridged Polkadot token contract, transferring admin rights to the attacker's address. With admin 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 around 108.2 ETH across multiple swaps at slightly different prices.
Low 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, and the attacker received 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 confirmed 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 attack vector.