Attacker Exploits Polkadot Token Vulnerability on Ethereum, Nets Only $250,000

While cryptocurrency hacks are common, instances where attackers take significant risks only to gain minimal rewards are rare. Such a scenario unfolded on Sunday when an attacker exploited a vulnerability in Hyperbridge's cross-chain gateway, connecting various blockchains, and minted 1 billion Polkadot tokens, valued at $1.19 billion, on Ethereum, but only managed to 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, not Polkadot's core network, with the native DOT token remaining unaffected. The vulnerability was found in how Hyperbridge's EthereumHost contract validates incoming cross-chain messages before passing them to the TokenGateway. Bridges, which facilitate the movement 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, making them vulnerable to attacks.

The attack began with the submission of a forged message via dispatchIncoming, which was then routed to TokenGateway.onAccept. However, 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 and sold them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting roughly 108.2 ETH.

The limited liquidity of the bridged DOT pool on Ethereum worked against the attacker, capping their profit. 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.

The exploit was flagged by CertiK, confirming the attack vector as the Hyperbridge gateway contract, with the attacker profiting approximately $237,000. Hyperbridge has yet to publicly comment on the exploit or disclose whether other bridged token contracts using the same gateway are vulnerable to similar attacks.