While cryptocurrency hacks are common, instances where attackers take significant risks only to gain minimal rewards are rare. One such incident occurred on Sunday, where an attacker exploited a vulnerability in Hyperbridge's cross-chain gateway, connecting different blockchains, to mint 1 billion Polkadot tokens, valued at $1.19 billion, on Ethereum, and then sold them for approximately $237,000 worth of ether. This exploit highlights the growing list of bridge vulnerabilities in 2026, including a $270 million Drift Protocol breach on Solana last month. The attack targeted the bridge contract, not Polkadot's core network, and the native token DOT 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, are often the weakest link in cross-chain architecture due to their admin-level control over token contracts on destination chains, making them vulnerable to validation failures that can grant attackers unlimited supply. The attack began 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 and sold them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting roughly 108.2 ETH across multiple swaps.
However, the limited liquidity in the bridged DOT pool on Ethereum worked against the attacker, capping their profit. The bridged DOT pool held limited depth, causing the 1 billion tokens to overwhelm the available liquidity, resulting in the attacker receiving only a fraction of a cent per token.
On a deeper pool or a higher-value bridged asset, the same vulnerability would have led to significantly larger losses. As of Monday morning, DOT traded 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.