While cryptocurrency hacks are not uncommon, instances where attackers take significant risks only to walk away with minimal gains are rare. Such a 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 Ethereum. The attacker then dumped these tokens for approximately $237,000 in ether. This exploit joins a growing list of bridge vulnerabilities in 2026, including last month's $270 million Drift Protocol incident on Solana and a social engineering attack that compromised infrastructure.
The Sunday attack targeted the bridge contract, specifically the EthereumHost contract, and not Polkadot's core network, meaning the native DOT token was unaffected. The vulnerability lay in how the contract validated incoming cross-chain messages before passing them to the TokenGateway.
Bridges, designed to facilitate the transfer of coins between different blockchains, remain a weak point in cross-chain architecture due to their admin-level control over token contracts on destination chains, making them susceptible to validation failures that can grant attackers unlimited supply. The attack unfolded when the attacker submitted 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 either absent or circumventable proof validation for this specific call path. The gateway processed the message as legitimate, resulting in the execution of changeAdmin on the bridged Polkadot token contract and transferring admin rights to the attacker's address. With this 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. Typically, weak liquidity is a major issue for large traders, but in this case, it prevented the attacker from realizing the full potential of their exploit. The bridged DOT 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 similar forged-message attacks.