Cryptocurrency hacks have become all too common, but it's rare for attackers to take huge risks and end up with relatively modest gains. However, that's exactly what happened on Sunday when an attacker exploited a vulnerability in Hyperbridge's cross-chain gateway, connecting different blockchain networks.
The attacker successfully minted 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network and then sold them for approximately $237,000 worth of ether. This exploit highlights the growing list of bridge vulnerabilities in 2026, including a $270 million Drift Protocol incident on Solana last month.
The Sunday attack targeted the bridge contract, not Polkadot's core network, and the native DOT token remained unaffected. The vulnerability lay 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 blockchain networks, 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 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. This allowed the gateway to process the message as legitimate.
The accepted message then executed a 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 Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting roughly 108.2 ETH across multiple swaps.
The low liquidity of the bridged DOT pool on Ethereum worked against the attacker, capping their profit. If the same vulnerability had been exploited on a deeper pool or a higher-value bridged asset, the losses would have been significantly larger.
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 the same forged-message attack vector.