Attacker Exploits Polkadot Token Vulnerability on Ethereum, But Walks Away with Modest $250,000

While cryptocurrency hacks are common, instances where attackers take significant risks only to gain minimal rewards are rare. Such a scenario unfolded on Sunday when an attacker exploited a vulnerability in the Hyperbridge cross-chain gateway, connecting various blockchains, to mint 1 billion Polkadot tokens on Ethereum, valued at $1.19 billion, and sell them for approximately $237,000 in 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 and not Polkadot's core network, leaving the native DOT token unaffected.

The vulnerability lay in the validation process of incoming cross-chain messages by Hyperbridge's EthereumHost contract before passing them to the TokenGateway. Bridges, which facilitate the movement 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 involved submitting a forged message via dispatchIncoming, routed to TokenGateway.onAccept, which lacked proper proof validation, allowing the gateway to process the message as legitimate.

This executed a changeAdmin function on the bridged Polkadot token contract, transferring admin rights to the attacker, who then minted 1 billion tokens and sold them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting around 108.2 ETH. However, the attacker's profit was capped due to weak liquidity in the bridged DOT pool on Ethereum, which was overwhelmed by the 1 billion tokens, resulting in the attacker receiving only a fraction of a cent per token.

This limited depth worked against the attacker, unlike usual scenarios where it poses a challenge for large traders. The exploit was flagged by CertiK, confirming the attack vector and the attacker's profit of approximately $237,000.

Hyperbridge has not publicly commented on the incident or disclosed whether other bridged token contracts using the same gateway are vulnerable to similar attacks.