Cryptocurrency hacks are a common occurrence, but instances where attackers take significant risks only to gain minimal rewards are rare. This unusual scenario unfolded on Sunday when an attacker exploited a vulnerability in Hyperbridge's cross-chain gateway, which connects various blockchains, resulting in the minting of 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network.
The attacker then sold these tokens for approximately $237,000 worth of ether. This incident highlights the growing list of bridge vulnerabilities in 2026, following a $270 million Drift Protocol drain on Solana last month. The exploit targeted the bridge contract, not Polkadot's core network, and the native token DOT 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 supply. The attack began with the attacker submitting a forged message via dispatchIncoming, which was then 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.
This resulted in the attacker gaining admin rights to the bridged Polkadot token contract, enabling them to mint 1 billion tokens in a single transaction. The tokens were then routed through Odos Router V3 into a Uniswap V4 DOT-ETH pool, from which the attacker extracted roughly 108.2 ETH across multiple swaps at different prices. However, 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.
On a deeper pool or with a higher-value bridged asset, the same vulnerability could have led to significantly larger losses. As of Monday morning, DOT was trading just under $1.20. CertiK identified the exploit, confirming 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 attack vector.