Cryptocurrency hacks have become all too familiar, but it's rare for attackers to take huge risks only to end up with relatively modest gains. However, that's exactly what happened on Sunday. An attacker found a vulnerability in Hyperbridge's cross-chain gateway, which connects various blockchains, and used it to mint 1 billion Polkadot tokens, worth $1.19 billion, on the Ethereum network. The attacker then sold these tokens for approximately $237,000 in ether.

This exploit is the latest in a series of bridge vulnerabilities that have been exposed in 2026, including a $270 million drain on Solana's Drift Protocol last month. The Sunday attack targeted the bridge contract, not Polkadot's core network, and the native DOT token was not affected. The vulnerability lay in how Hyperbridge's EthereumHost contract validated incoming cross-chain messages before passing them to the TokenGateway. Bridges, which facilitate the movement of coins between different blockchains, remain a weak point in cross-chain architecture because they have admin-level control over token contracts on destination chains.

This means that a single validation failure can grant an attacker unlimited control. The attack unfolded when the attacker submitted a forged message via dispatchIncoming, which was then routed to TokenGateway.onAccept.

The request receipts check failed to verify the message against a valid cross-chain state commitment from Polkadot, and the gateway processed the message as legitimate. The accepted message executed a changeAdmin function 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. However, the attacker's profit was limited due to weak liquidity in the bridged DOT pool on Ethereum.

The pool's limited depth meant that 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 flagged 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.