While cryptocurrency hacks are a common occurrence, it is rare for attackers to take significant risks and walk away with relatively modest gains. However, this unusual scenario unfolded on Sunday when an attacker exploited a vulnerability in a cross-chain gateway, minting 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network, and subsequently selling them for around $237,000 worth of ether. This incident is the latest in a series of bridge vulnerabilities that have been exposed in 2026, including a $270 million exploit on the Drift Protocol on Solana last month. The attack targeted the bridge contract, rather than Polkadot's core network, and the native DOT token remained unaffected.
The vulnerability was found in the validation process for incoming cross-chain messages in the Hyperbridge EthereumHost contract, which, when compromised, can grant an attacker administrative control over token contracts on the destination chain. Bridges are particularly vulnerable because they hold administrative-level control over token contracts on the destination chain, making them the weakest link in cross-chain architecture. The attack began when the perpetrator submitted a forged message via the dispatchIncoming function, which was then routed to the TokenGateway.onAccept function.
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, indicating that the proof validation was either absent or could be circumvented. As a result, the gateway processed the message as legitimate, and the accepted message executed the changeAdmin function on the bridged Polkadot token contract, transferring administrative rights to the attacker's address. With administrative control, the attacker minted 1 billion tokens in a single transaction and routed them through the Odos Router V3 into a Uniswap V4 DOT-ETH pool, ultimately extracting around 108.2 ETH across multiple swaps at slightly different prices. The limited liquidity in the bridged DOT pool on Ethereum worked against the attacker, capping their profit.
The 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 same 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 below $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 yet to publicly comment on the exploit or disclose whether other bridged token contracts using the same gateway are vulnerable to the same forged-message attack vector.