Attacker Exploits Cross-Chain Vulnerability, Mints $1 Billion in Polkadot Tokens but Only Gains $250,000

While cryptocurrency hacks are becoming increasingly common, instances where attackers take substantial risks only to gain minimal rewards are rare. Such a scenario unfolded on Sunday when an attacker exploited a weakness in the Hyperbridge cross-chain gateway, connecting various blockchains, and minted 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network. However, the attacker only managed to sell these tokens for approximately $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 targeted bridge contract, rather than Polkadot's core network, contained the vulnerability, specifically in how the Hyperbridge's EthereumHost contract validated incoming cross-chain messages before passing them to the TokenGateway. Bridges, which facilitate the transfer of coins between different blockchains, remain a weak point in cross-chain architecture due to their admin-level control over token contracts on destination chains, making them susceptible to attacks that can grant unlimited token minting capabilities. The attack began 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. This led to the attacker gaining admin rights to the bridged Polkadot token contract, enabling them to mint 1 billion tokens and sell them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, ultimately extracting around 108.2 ETH. The limited liquidity in the bridged DOT pool on Ethereum worked against the attacker, capping their profit. If the same vulnerability were exploited on a deeper pool or a higher-value bridged asset, the losses would have been significantly greater.

As of Monday morning, DOT was trading just below $1.20. The exploit was flagged by CertiK, which confirmed the attack vector was the Hyperbridge gateway contract, resulting in the attacker gaining 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 similar attacks.