The world of cryptocurrency is no stranger to hacking incidents, but it's rare for attackers to take huge risks only to walk away with modest gains. Such a scenario unfolded recently when an attacker exploited a weakness in Hyperbridge's cross-chain gateway, which connects different blockchain networks.
By doing so, the attacker was able to mint 1 billion Polkadot tokens on the Ethereum network, valued at approximately $1.19 billion, and then sell them for around $237,000 in ether. This incident highlights the ongoing issue of bridge vulnerabilities in 2026, following a $270 million drain on Solana's Drift Protocol last month and a social engineering attack that compromised infrastructure. The latest exploit targeted the bridge contract rather than Polkadot's core network, leaving the native DOT token 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, remain a weak point 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, instead storing an all-zeros commitment value. This allowed the gateway to process the message as legitimate. The accepted message then executed changeAdmin on the bridged Polkadot token contract, transferring admin rights to the attacker's address.
With this 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 around 108.2 ETH across multiple swaps. Interestingly, the limited liquidity in the market worked against the attacker, capping their potential profit. The bridged DOT pool on Ethereum had limited depth, meaning the 1 billion tokens overwhelmed the available liquidity, resulting in the attacker receiving only a fraction of a cent per token. If this 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. The exploit was flagged by CertiK, which 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 yet to publicly comment on the exploit or disclose whether other bridged token contracts using the same gateway are vulnerable to the same attack vector.