Attacker Exploits Cross-Chain Vulnerability, Mints $1 Billion in Polkadot Tokens but Only Profits $250,000

Cryptocurrency hacks have become increasingly common, but 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 to mint 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network. The attacker then sold these tokens for around $237,000 worth of ether. This exploit highlights the growing list of bridge vulnerabilities in 2026, including a $270 million drain on Solana's Drift Protocol last month.

The attack targeted the bridge contract, not Polkadot's core network, and the native DOT token remained unaffected. The vulnerability stemmed from the validation process of incoming cross-chain messages in Hyperbridge's EthereumHost contract. 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 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 and sold them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting around 108.2 ETH. However, the limited liquidity in the bridged DOT pool on Ethereum worked against the attacker, capping their profit. The same vulnerability could have resulted in significantly larger losses if it had been exploited on a deeper pool or a higher-value bridged asset.

The incident was flagged by CertiK, confirming the attack vector and the attacker's profit of approximately $237,000. 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.