Attacker Exploits Polkadot Token Vulnerability on Ethereum, but Gains are Limited

While crypto hacks are a common occurrence, it's rare for attackers to take significant risks and end up with relatively modest gains. However, that's exactly what happened on Sunday when an attacker exploited a vulnerability in Hyperbridge's cross-chain gateway, which connects different blockchains, to mint 1 billion Polkadot tokens on Ethereum, valued at $1.19 billion, and then sold them for approximately $237,000 worth of ether. This incident highlights the growing issue of bridge vulnerabilities in 2026, following a $270 million Drift Protocol drain on Solana last month.

The exploit targeted the bridge contract, rather than Polkadot's core network, and the native token DOT remained unaffected. The vulnerability was found in how Hyperbridge's EthereumHost contract validates incoming cross-chain messages before passing them to the TokenGateway. Bridges, which facilitate the transfer of coins between blockchains, are often the weakest link in cross-chain architecture, as they hold admin-level control over token contracts on destination chains, making them vulnerable to attacks.

In this case, the attacker submitted a forged message via dispatchIncoming, which was routed to TokenGateway.onAccept, and due to a lack of proper validation, the gateway processed the message as legitimate. The accepted message then executed changeAdmin on the bridged Polkadot token contract, transferring admin rights to the attacker's address, allowing them to mint 1 billion tokens and sell them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting around 108.2 ETH. However, the limited liquidity in the bridged DOT pool on Ethereum meant that the attacker was only able to receive a fraction of a cent per token, capping their profit. If the vulnerability had been exploited on a deeper pool or a higher-value bridged asset, the losses could have been significantly larger.

The incident was flagged by CertiK, which confirmed that 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 the same forged-message attack vector.