Attacker Exploits Hyperbridge Vulnerability, Steals $250,000 in Polkadot Token Heist

While cryptocurrency hacks are becoming increasingly common, it's rare for attackers to take significant risks and walk away with relatively modest gains. However, that's exactly what happened on Sunday when an attacker exploited a vulnerability in the Hyperbridge cross-chain gateway, connecting various blockchains, to mint 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network and sell them for approximately $237,000 in ether. This incident is the latest in a series of bridge vulnerabilities in 2026, including a $270 million exploit on Solana's Drift Protocol last month.

The attack targeted the bridge contract rather than Polkadot's core network, leaving the native DOT token unaffected. The vulnerability was found in the way Hyperbridge's EthereumHost contract validates 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 then routed to TokenGateway.onAccept.

However, 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, granting the attacker admin rights. With these rights, the attacker minted 1 billion tokens in a single transaction and sold them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, earning roughly 108.2 ETH. The limited liquidity in 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 greater. The price of DOT was just under $1.20 during Asian morning hours on Monday.

CertiK identified the exploit, confirming that 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 yet to publicly comment on the exploit or disclose whether other bridged token contracts using the same gateway are vulnerable to the same attack.