Attacker Exploits Hyperbridge Vulnerability, Mints $1 Billion in Polkadot Tokens but Only Nets $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, connecting various blockchains, and minted 1 billion Polkadot tokens on Ethereum, valued at $1.19 billion, but only managed to sell them 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 token DOT remained 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. 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, and the gateway processed 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. However, the limited liquidity of the bridged DOT pool on Ethereum worked against the attacker, capping their profit. The attacker's gains were significantly reduced due to the overwhelming amount of tokens flooding the market, resulting in a fraction of a cent per token. CertiK flagged the exploit, confirming the attack vector was the Hyperbridge gateway contract, and the attacker profited approximately $237,000 from minting and selling the bridged tokens.

Hyperbridge has yet to publicly comment on the exploit or disclose whether other bridged token contracts using the same gateway are vulnerable to the same attack vector.