Cryptocurrency hacks have become all too familiar, but instances where attackers take significant risks only to reap relatively modest rewards are rare. Such a 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 subsequently sold them for approximately $237,000 worth of ether. This incident adds to the growing list of bridge vulnerabilities in 2026, following a $270 million exploit on Solana's Drift Protocol last month. The attack targeted the bridge contract, specifically the EthereumHost contract's validation process for incoming cross-chain messages, rather than Polkadot's core network.
As a result, Polkadot's native token, DOT, remained unaffected. The vulnerability allowed the attacker to bypass state proof validation, granting them admin control over the bridged DOT token. Bridges, designed to facilitate the transfer of coins between different 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 potentially allow an attacker to mint an unlimited supply of tokens. The attack began with the submission of 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, processing the message as legitimate instead.
This allowed the attacker to execute changeAdmin on the bridged Polkadot token contract, transferring admin rights to their 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 roughly 108.2 ETH. Notably, the limited liquidity in the bridged DOT pool on Ethereum worked against the attacker, capping their profit.
Typically, weak liquidity is a significant issue for large traders, but in this case, it prevented the attacker from selling the tokens at a favorable price. The bridged DOT pool's limited depth meant that the 1 billion tokens overwhelmed the available liquidity, resulting in the attacker receiving only 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 could have been significantly larger. As of Monday morning, DOT was trading just under $1.20.
The exploit was flagged by CertiK, which confirmed that 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 forged-message attack vector.