While crypto hacks are a common occurrence, instances where attackers take significant risks only to gain minimal rewards are rare. This unusual scenario unfolded on Sunday when an attacker exploited a vulnerability in Hyperbridge's cross-chain gateway, which connects different blockchains, to mint 1 billion Polkadot tokens, valued at $1.19 billion, on Ethereum. The attacker then sold these tokens for around $237,000 worth of ether. This exploit is the latest in a series of bridge vulnerabilities in 2026, following a $270 million Drift Protocol drain on Solana last month.
The Sunday attack targeted the bridge contract, not Polkadot's core network, and the native token DOT remained unaffected. The vulnerability was found in how Hyperbridge's EthereumHost contract verifies incoming cross-chain messages before passing them to the TokenGateway. Bridges, which facilitate the transfer of coins between blockchains, are often the weakest link in cross-chain architecture due to their admin-level control over token contracts on destination chains. A single validation failure can grant an attacker the ability to mint an unlimited supply of tokens.
The attack began when the hacker 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, allowing the gateway to process the message as legitimate. The accepted message executed changeAdmin on the bridged Polkadot token contract, giving the attacker admin rights. With these rights, the attacker minted 1 billion tokens in a single transaction and sold them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, earning roughly 108.2 ETH.
However, the attacker's profit was limited due to the weak liquidity in the bridged DOT pool on Ethereum. The 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 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.