While cryptocurrency hacks are common, instances where attackers take significant risks only to gain minimal rewards are rare. Such a scenario occurred on Sunday, when an attacker exploited a vulnerability in the Hyperbridge cross-chain gateway, which connects multiple blockchains, resulting in the minting of 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 incident is the latest in a series of bridge vulnerabilities that have been exposed in 2026, including a $270 million drain from the Drift Protocol on Solana last month and a social engineering attack that compromised infrastructure. The Sunday attack targeted the bridge contract rather than Polkadot's core network, leaving the native DOT token unaffected. The vulnerability was found in the way Hyperbridge's EthereumHost contract validated incoming cross-chain messages before passing them to the TokenGateway.
Bridges are particularly vulnerable as they hold admin-level control over token contracts on destination chains, meaning a single validation failure can grant an attacker unlimited minting capabilities. The attack began with the submission of 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, instead storing an all-zeros commitment value, indicating that proof validation was either absent or could be circumvented for this specific call path. As a result, the gateway processed the message as legitimate.
The accepted message then 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 routed them through Odos Router V3 into a Uniswap V4 DOT-ETH pool, extracting roughly 108.2 ETH across multiple swaps at slightly different prices.
The limited liquidity of the bridged DOT pool on Ethereum worked against the attacker, capping their profit. The pool's weak depth meant that the 1 billion tokens overwhelmed the available liquidity, resulting in the attacker receiving only a fraction of a cent per token. In a deeper pool or with a higher-value bridged asset, the same vulnerability would have led to significantly larger losses. As of Monday morning, DOT was trading just under $1.20.
The exploit was flagged by CertiK, which confirmed that 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 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.