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

Cryptocurrency hacks have become increasingly common, but 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 the Hyperbridge cross-chain gateway, connecting various blockchains, to mint 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network, and subsequently sold them for around $237,000 worth of ether. This exploit highlights the growing list of bridge vulnerabilities in 2026, including the $270 million Drift Protocol incident on Solana last month. The attack targeted the bridge contract, leaving Polkadot's core network and native token DOT unaffected.

The vulnerability was found in the Hyperbridge EthereumHost contract's validation process for incoming cross-chain messages. Bridges, which facilitate the transfer of coins between blockchains, remain a weak point 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 began with the submission of a forged message via dispatchIncoming, which was 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 around 108.2 ETH.

The limited liquidity of the bridged DOT pool on Ethereum worked against the attacker, capping their profit. The attack would have resulted in significantly larger losses if it had occurred on a deeper pool or a higher-value bridged asset. As of Monday morning, DOT trades just under $1.20. CertiK confirmed the exploit, stating that the attacker profited 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 the same attack vector.