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

While cryptocurrency hacks are not uncommon, instances where attackers take significant risks only to gain minimal rewards are rare. Such a scenario occurred on Sunday when an attacker exploited a vulnerability in Hyperbridge's cross-chain gateway, which connects different blockchains. The attacker successfully minted 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network and then sold them for roughly $237,000 worth of ether.

This incident highlights the growing list of bridge vulnerabilities in 2026, including a $270 million exploit on Solana's Drift Protocol last month. The Sunday attack targeted the bridge contract, not Polkadot's core network, and the native DOT token remained unaffected. The vulnerability was found in the validation process of incoming cross-chain messages by Hyperbridge's EthereumHost contract before passing them to the TokenGateway. 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 supply. The attack unfolded when the attacker submitted 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, and the gateway processed the message as legitimate.

The accepted message executed changeAdmin on the bridged Polkadot token contract, transferring admin rights to the attacker's address. With admin control, the attacker minted 1 billion tokens in a single transaction 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. If the same vulnerability were to be exploited 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 was the Hyperbridge gateway contract and that the attacker profited around $237,000 from minting and selling 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.