Attacker Exploits Vulnerability in Hyperbridge's Cross-Chain Gateway, Steals $250,000

While cryptocurrency hacks are commonplace, it's rare for attackers to take significant risks and walk away with relatively minor gains. However, this unusual scenario unfolded on Sunday when an attacker exploited a vulnerability in Hyperbridge's cross-chain gateway. The attacker successfully minted 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network and sold them for around $237,000 in ether.

This incident adds to the growing list of bridge vulnerabilities in 2026, which includes a $270 million Drift Protocol exploit 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 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 minting capabilities. 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, 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 in a single transaction and sold them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting approximately 108.2 ETH across multiple swaps. 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 larger.

As of Monday morning, DOT was trading just under $1.20. CertiK confirmed the attack vector was the Hyperbridge gateway contract and the attacker's profit was 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.