Attacker Exploits Polkadot Token Vulnerability on Ethereum, 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 multiple blockchains, to mint 1 billion Polkadot tokens on Ethereum and sell them for approximately $237,000 in ether. This exploit highlights the growing list of bridge vulnerabilities in 2026, including a $270 million Drift Protocol incident on Solana last month. The attack targeted the bridge contract rather than Polkadot's core network, leaving the native DOT token 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 roughly 108.2 ETH. However, limited liquidity in the bridged DOT pool on Ethereum capped the attacker's profit, as the 1 billion tokens overwhelmed the available liquidity, resulting in 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. The attack was flagged by CertiK, confirming the Hyperbridge gateway contract as the attack vector, with the attacker profiting 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.