While cryptocurrency hacks are commonplace, instances where attackers take significant risks only to reap minimal rewards are unusual. Such a scenario unfolded on Sunday, as an attacker exploited a vulnerability in Hyperbridge's cross-chain gateway, which connects multiple blockchains, to mint 1 billion Polkadot tokens ($1.19 billion) on Ethereum and sell them for approximately $237,000 worth of ether. This exploit is the latest in a series of bridge vulnerabilities exposed in 2026, including a $270 million Drift Protocol hack on Solana last month.
The attack targeted the bridge contract, not Polkadot's core network, and the native DOT token remained 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 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 grant an attacker unlimited minting capabilities. 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, instead storing an all-zeros commitment value, indicating that proof validation was either absent or circumventable for this specific call path.
The gateway processed the message as legitimate, executing changeAdmin on the bridged Polkadot token contract and 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 Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting roughly 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 weak 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.