Hacker Exploits Cross-Chain Vulnerability, Steals $250,000 Despite Minting $1 Billion in Polkadot Tokens

Crypto attacks are commonplace, but instances where attackers take significant risks only to gain minimal rewards are rare. One such case occurred on Sunday, when an attacker exploited a vulnerability in the Hyperbridge cross-chain gateway to mint 1 billion Polkadot tokens, worth $1.19 billion, on the Ethereum network, and then sold them for approximately $237,000 in ether. This incident highlights the ongoing issue of bridge vulnerabilities in 2026, following a $270 million exploit on Solana's Drift Protocol last month. The attack targeted the bridge contract, rather than Polkadot's core network, and the native DOT token remained 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, 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 grant an attacker unlimited minting capabilities. The attack unfolded when the hacker submitted 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 granted the attacker admin rights to the bridged Polkadot token contract, enabling them to mint 1 billion tokens and sell them through Odos Router V3 and Uniswap V4, resulting in roughly 108.2 ETH. However, the attacker's profit was limited due to weak liquidity in the bridged DOT pool on Ethereum, which was overwhelmed by the large number of tokens. The lack of depth in the market meant the attacker received only a fraction of a cent per token.

If the vulnerability had been exploited on a deeper pool or a higher-value bridged asset, the losses could have been significantly greater. As of Monday morning, DOT was trading just below $1.20.

CertiK confirmed the attack vector was the Hyperbridge gateway contract and 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 similar attacks.