Hacker Exploits Polkadot Token Vulnerability, but Profits Are Limited

Cryptocurrency hacks are a common occurrence, 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 Hyperbridge's cross-chain gateway, connecting various blockchains, to mint 1 billion Polkadot tokens on Ethereum and sell them for approximately $237,000 in ether. This incident highlights the growing list of bridge vulnerabilities in 2026, following a $270 million Drift Protocol hack on Solana last month. The Sunday exploit targeted the bridge contract, not Polkadot's core network, and the native token DOT remained unaffected.

The vulnerability was found in how Hyperbridge's EthereumHost contract validated 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 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 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, 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 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. If the vulnerability had been exploited on a deeper pool or a higher-value bridged asset, the losses would have been significantly larger. CertiK identified the exploit, confirming the attack vector was the Hyperbridge gateway contract, and 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.