Attacker Exploits Hyperbridge Vulnerability, Steals $250,000 Despite Minting $1 Billion in Polkadot Tokens

Cryptocurrency hacks have become increasingly common, but instances where attackers take significant risks only to gain minimal rewards are rare. One such incident occurred on Sunday, where an attacker exploited a vulnerability in Hyperbridge's cross-chain gateway, connecting multiple 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 highlights the growing list of bridge vulnerabilities in 2026, including a $270 million Drift Protocol exploit on Solana last month. The Sunday attack targeted the bridge contract, leaving Polkadot's core network and its native token DOT unaffected. The vulnerability stemmed from the validation process of incoming cross-chain messages in Hyperbridge's EthereumHost contract.

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. A single validation failure can grant an attacker unlimited supply. The attack involved the submission of a forged message via dispatchIncoming, which was 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 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 in a single transaction and sold them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting roughly 108.2 ETH.

However, limited liquidity 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 with a higher-value bridged asset, the same vulnerability could have led to significantly larger losses. As of Monday morning, DOT was trading just under $1.20. CertiK 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.