Attacker Exploits Polkadot Token Bridge, Nets Only $250,000 Despite Minting $1 Billion

Cryptocurrency hacks have become commonplace, but instances where attackers take significant risks only to reap minimal rewards are rare. One such incident occurred on Sunday, where an attacker exploited a vulnerability in Hyperbridge's cross-chain gateway to mint 1 billion Polkadot tokens, valued at $1.19 billion, on the Ethereum network, but ultimately only managed to sell 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 exploit on Solana last month. The attack targeted the bridge contract, not Polkadot's core network, and the native DOT token remained unaffected.

The vulnerability was found in 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 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, allowing the gateway to process the message as legitimate. The accepted message granted the attacker admin rights to the bridged Polkadot token contract, enabling them to mint 1 billion tokens and sell them through Odos Router V3 and Uniswap V4, resulting in roughly 108.2 ETH.

The limited liquidity of the bridged DOT pool on Ethereum worked against the attacker, capping their profit. If the same vulnerability were to be exploited on a deeper pool or a higher-value bridged asset, the losses would have been significantly larger.

The incident was flagged by CertiK, which confirmed the attack vector and the attacker's profit of approximately $237,000. Hyperbridge has not publicly commented on the exploit or disclosed whether other bridged token contracts using the same gateway are vulnerable to the same attack vector.