Attacker Exploits Polkadot Token Vulnerability on Ethereum, Nets Only $250,000

Cryptocurrency hacks have become increasingly common, but instances where attackers take significant risks only to gain minimal rewards are rare. One such incident occurred on Sunday, where an attacker exploited a vulnerability in Hyperbridge's cross-chain gateway, which connects multiple blockchains, to mint 1 billion Polkadot tokens on Ethereum and sell them for approximately $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. 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 way 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 validation failures that can grant attackers unlimited supply. The attack unfolded when the attacker submitted a forged message via dispatchIncoming, which was 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 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 and sold them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting roughly 108.2 ETH. However, the limited liquidity of the bridged DOT pool on Ethereum worked against the attacker, capping their profit. The attacker's gain was significantly reduced due to the overwhelmed available liquidity, resulting in 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 would have been significantly larger.

As of Monday morning, DOT trades just under $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 not publicly commented on the exploit or disclosed whether other bridged token contracts using the same gateway are vulnerable to the same attack vector.