Attacker Exploits Polkadot Token Vulnerability on Ethereum, Nets Only $250,000

Cryptocurrency hacks have become commonplace, but instances where attackers take substantial risks only to gain minimal rewards are rare. One such incident occurred on Sunday, when an attacker exploited a weakness in Hyperbridge's cross-chain gateway, which connects various blockchains, to mint 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network. The attacker then sold these tokens for approximately $237,000 in ether.

This exploit is the latest in a series of bridge vulnerabilities in 2026, including a $270 million Drift Protocol exploit on Solana last month. The Sunday attack targeted the bridge contract, rather than Polkadot's core network, and the native DOT token remained unaffected.

The vulnerability lay in the EthereumHost contract's validation process for incoming cross-chain messages. 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 supply. The attack began 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, allowing the gateway to process the message as legitimate. The accepted message executed changeAdmin on the bridged Polkadot token contract, transferring admin rights to the attacker's address. With admin control, the attacker minted 1 billion tokens and sold them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting roughly 108.2 ETH. The limited liquidity in 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. Hyperbridge has yet to comment publicly on the exploit or disclose whether other bridged token contracts using the same gateway are vulnerable to the same attack vector.