Attacker Exploits Polkadot Token Vulnerability on Ethereum, Gains Limited Profit

Cryptocurrency hacks have become increasingly common, 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 blockchain. However, due to poor market liquidity, the attacker was only able to sell the tokens for approximately $237,000 worth of ether.

This exploit highlights the ongoing issue of bridge vulnerabilities in 2026, following a $270 million Drift Protocol drain on Solana last month. The attack targeted the bridge contract, rather than Polkadot's core network, and the native DOT token remained unaffected. The vulnerability lay in the validation process of incoming cross-chain messages, which allowed the attacker to submit a forged message and gain admin-level control over the bridged token contract. As a result, the attacker was able to mint an unlimited supply of tokens.

The attack unfolded when the attacker submitted a forged message via the dispatchIncoming function, which was routed to the TokenGateway.onAccept function. 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 the changeAdmin function 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 a Uniswap V4 DOT-ETH pool, extracting roughly 108.2 ETH.

The limited liquidity in the market worked against the attacker, capping their profit. The bridged DOT pool on Ethereum had limited 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.

On a deeper pool or a higher-value bridged asset, the same vulnerability would have resulted in significantly larger losses. The exploit was flagged by CertiK, which confirmed the attack vector was the Hyperbridge gateway contract and that the attacker profited approximately $237,000 from minting and selling the bridged tokens. 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.