Hacker Exploits Polkadot Tokens on Ethereum, but Walks Away with Minimal Gains

While cryptocurrency hacks are a regular occurrence, instances where attackers take significant risks only to reap minimal rewards are rare. One such incident occurred on Sunday, where an attacker leveraged a vulnerability in Hyperbridge's cross-chain gateway to mint 1 billion Polkadot tokens on Ethereum, valued at $1.19 billion, and then sold them for approximately $237,000 in ether. This exploit joins a growing list of bridge vulnerabilities in 2026, including a $270 million Drift Protocol incident on Solana last month.

The attack targeted the bridge contract, not Polkadot's core network, and did not affect the native DOT token. The weakness lay in how Hyperbridge's EthereumHost contract validated incoming cross-chain messages before passing them to the TokenGateway. Bridges, which facilitate the transfer of coins between blockchains, remain a weak point in cross-chain architecture due to their admin-level control over token contracts on destination chains.

The attack unfolded when the attacker submitted a forged message via dispatchIncoming, which was then routed to TokenGateway.onAccept. 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 then executed changeAdmin 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.

However, the limited liquidity in the market worked against the attacker, capping their profit. The bridged DOT pool on Ethereum had shallow depth, causing the 1 billion tokens to overwhelm the available liquidity and resulting in the attacker receiving 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 would have been significantly larger. As of Monday morning, DOT was trading just under $1.20. CertiK confirmed the exploit, identifying the Hyperbridge gateway contract as the attack vector and estimating the attacker's profit at around $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 attack vector.