Attacker Exploits Hyperbridge Vulnerability, Mints $1 Billion in Polkadot Tokens but Only Profits $250,000

While cryptocurrency hacks are commonplace, instances where attackers take significant risks only to gain minimal profits are rare. Such a scenario occurred on Sunday when an attacker exploited a vulnerability in Hyperbridge's cross-chain gateway, connecting various blockchains, to mint 1 billion Polkadot tokens on Ethereum, valued at $1.19 billion, and subsequently sold them for roughly $237,000 worth of ether.

This exploit highlights the growing list of bridge vulnerabilities in 2026, including a $270 million Drift Protocol incident on Solana last month and a social engineering attack involving compromised infrastructure. The targeted bridge contract, not Polkadot's core network, contained the vulnerability, specifically in how Hyperbridge's EthereumHost contract validated incoming cross-chain messages before passing them to the TokenGateway. Bridges, facilitating coin transfers between blockchains, remain the weakest link in cross-chain architecture due to their admin-level control over token contracts on destination chains, making a single validation failure potentially catastrophic.

The attack unfolded with the submission of a forged message via dispatchIncoming, routed to TokenGateway.onAccept, where 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 execution of changeAdmin on the bridged Polkadot token contract, transferring admin rights to the attacker, who then minted 1 billion tokens and sold them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting approximately 108.2 ETH.

The limited liquidity of the bridged DOT pool on Ethereum worked against the attacker, capping their profit. The low liquidity meant that the 1 billion tokens overwhelmed the available liquidity, resulting in the attacker receiving only a fraction of a cent per token.

On a deeper pool or with a higher-value bridged asset, the same vulnerability could have led to significantly larger losses. As of Monday morning, DOT traded just under $1.20. CertiK identified the exploit, confirming the attack vector was the Hyperbridge gateway contract, with the attacker profiting around $237,000 from the minting and sale of the bridged tokens. 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.