While cryptocurrency hacks are a common occurrence, instances where attackers take significant risks only to reap minimal rewards are rare. One such instance occurred on Sunday, when an attacker exploited a vulnerability in the Hyperbridge 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 roughly $237,000 worth of ether. This exploit is the latest in a series of bridge vulnerabilities that have been uncovered in 2026, including a $270 million Drift Protocol hack on the Solana network last month.
The Sunday attack targeted the bridge contract, rather than Polkadot's core network, and did not affect the native DOT token. The vulnerability was found in the way Hyperbridge's EthereumHost contract validated incoming cross-chain messages before passing them to the TokenGateway. Bridges, which facilitate the transfer of coins between different blockchains, are often the weakest link in cross-chain architecture, as they hold admin-level control over token contracts on destination chains.
This means that a single validation failure can grant an attacker the ability to mint an unlimited supply of tokens. The attack unfolded when the attacker submitted a forged message via the dispatchIncoming function, which was then routed to the TokenGateway.onAccept function. The request receipts check, which should have verified the message against a valid cross-chain state commitment from Polkadot, failed to do so, allowing the gateway to process the message as legitimate.
The accepted message then executed the changeAdmin function 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 the Odos Router V3 and Uniswap V4 DOT-ETH pool, extracting approximately 108.2 ETH.
However, the attacker's profits were limited due to the weak liquidity in the bridged DOT pool on Ethereum, which 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.
The DOT token was trading at just under $1.20 as of Monday morning. CertiK, a blockchain security firm, flagged the exploit and confirmed that the attack vector was the Hyperbridge gateway contract, and that the attacker profited approximately $237,000 from the minting and sale of 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.