Attackers exploit Hyperbridge vulnerability to mint $1 billion in Polkadot tokens, but only net $250,000

Cryptocurrency hacks have become increasingly common, but it's rare for attackers to take significant risks and walk away with relatively modest gains. However, this is exactly what happened on Sunday when an attacker exploited a vulnerability in Hyperbridge's cross-chain gateway, which connects different blockchain networks. The attacker managed to mint 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network and sold them for roughly $237,000 worth of ether.

This incident highlights the growing list of bridge vulnerabilities in 2026, including a $270 million Drift Protocol exploit on Solana last month. The attack targeted the bridge contract, rather than Polkadot's core network, and the native DOT token was not affected. The vulnerability was found in the way Hyperbridge's EthereumHost contract validates incoming cross-chain messages before passing them to the TokenGateway.

Bridges are often the weakest link in cross-chain architecture, as they hold administrative control over token contracts on destination chains, making them a prime target for attackers. 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, granting 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, extracting approximately 108.2 ETH. However, the limited liquidity in the bridged DOT pool on Ethereum worked against the attacker, capping their profits. If the attack had occurred 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 confirmed the exploit, stating 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 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.