While cryptocurrency hacks are not unusual, cases where attackers take significant risks only to gain minimal rewards are rare. Such a scenario occurred 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 Ethereum. These tokens were then dumped for roughly $237,000 in ether.
This incident adds to the growing list of bridge vulnerabilities in 2026, including a $270 million Drift Protocol exploit on Solana last month. The attack targeted the bridge contract, not Polkadot's core network, and the native DOT token was unaffected. The vulnerability lay in how Hyperbridge's EthereumHost contract validated incoming cross-chain messages 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.
This means 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 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, storing an all-zeros commitment value and suggesting that proof validation was either absent or circumventable for this specific call path.
The gateway processed the message as legitimate, and the accepted message executed changeAdmin 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 routed them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting approximately 108.2 ETH across multiple swaps at slightly different prices.
However, the limited liquidity of 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 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.