Cryptocurrency hacks are not unusual, but instances where attackers take significant risks only to gain minimal rewards are rare. Such a scenario unfolded on Sunday, when an attacker exploited a weakness in a cross-chain gateway to mint 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network, and then sold them for approximately $237,000 in ether. This incident highlights the ongoing issue of bridge vulnerabilities in 2026, following a $270 million exploit on Solana's Drift Protocol last month.
The attacked bridge contract, rather than Polkadot's core network, was the target, and the native DOT token remained unaffected. The vulnerability stemmed from the validation process of incoming cross-chain messages in Hyperbridge's EthereumHost contract.
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 minting capabilities. The attack began with the submission of a forged message, which was mistakenly processed as legitimate due to a missing or circumventable proof validation.
This allowed the attacker to gain admin rights over the bridged Polkadot token contract, mint 1 billion tokens, and then sell them through a Uniswap V4 pool, resulting in roughly 108.2 ETH. However, the limited liquidity of the bridged DOT pool on Ethereum worked against the attacker, capping their profit at a fraction of the potential value. If the same vulnerability were exploited on a deeper pool or a higher-value bridged asset, the losses would have been significantly greater. The incident was flagged by CertiK, confirming the attack vector and the attacker's profit of approximately $237,000.
Hyperbridge has yet to publicly comment on the exploit or disclose whether other bridged token contracts are vulnerable to the same attack vector.