Attacker Exploits Hyperbridge Vulnerability, Steals $250,000 in Polkadot Token Heist

Cryptocurrency hacks have become increasingly common, but instances where attackers take significant risks only to reap modest rewards are rare. One such incident occurred on Sunday, where an attacker exploited a vulnerability in the Hyperbridge cross-chain gateway, connecting various blockchains, to mint 1 billion Polkadot tokens on Ethereum, valued at $1.19 billion, and subsequently 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 drain on Solana last month. The attack targeted the bridge contract, not 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, which, when compromised, granted the attacker admin-level control over the token contract. Bridges, designed to 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 enable an attacker to mint an unlimited supply of tokens. The attack unfolded with the submission of a forged message via dispatchIncoming, which was then 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, the limited liquidity of the bridged DOT pool on Ethereum worked against the attacker, capping their profit. The attack highlights the importance of robust validation mechanisms in cross-chain gateways to prevent such exploits. According to CertiK, the attack vector was indeed the Hyperbridge gateway contract, and the attacker profited approximately $237,000 from the exploit. Hyperbridge has yet to publicly comment on the incident or disclose whether other bridged token contracts using the same gateway are vulnerable to similar attacks.