Cryptocurrency hacks have become all too familiar, but it's rare for attackers to take significant risks only to end up with relatively modest gains. However, that's exactly what happened on Sunday when an attacker exploited a vulnerability in the Hyperbridge cross-chain gateway, which connects various blockchains, to mint 1 billion Polkadot tokens on Ethereum, valued at $1.19 billion, and then sold them for approximately $237,000 in ether.
This incident is the latest in a string of bridge vulnerabilities that have been exposed in 2026, including a $270 million exploit on Solana's Drift Protocol last month and a social engineering attack that compromised infrastructure. The exploit targeted the bridge contract rather than Polkadot's core network, leaving the native DOT token unaffected. The vulnerability was found in how the Hyperbridge's EthereumHost contract verifies incoming cross-chain messages before passing them to the TokenGateway.
Bridges, which facilitate the transfer of coins between different blockchains, remain the weakest link in cross-chain architecture because they have admin-level control over token contracts on destination chains, meaning a single validation failure can give an attacker the power to mint an unlimited supply of tokens. The attack began when the attacker submitted a forged message via dispatchIncoming, which was then routed to TokenGateway.onAccept. The request receipts check, which should have verified the message against a valid cross-chain state commitment from Polkadot, failed to do so, allowing the gateway to process the message as legitimate. The accepted message then executed a changeAdmin function on the bridged Polkadot token contract, granting the attacker admin rights.
With these rights, 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 around 108.2 ETH across multiple swaps at slightly different prices. However, the limited liquidity in the bridged DOT pool on Ethereum worked against the attacker, capping their profits.
Normally, weak liquidity is a major issue for large traders, but in this case, it prevented the attacker from making more substantial gains. The bridged DOT pool held limited depth, meaning the 1 billion tokens overwhelmed the available liquidity, and the attacker received only a fraction of a cent per token. If the vulnerability had been exploited on a deeper pool or a higher-value bridged asset, the losses could have been significantly larger. As of Monday morning, DOT was trading just under $1.20.
The exploit was flagged by CertiK, which confirmed that the attack vector was the Hyperbridge gateway contract and that the attacker made 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 type of attack.