Hyperbridge vulnerability enables minting of 1B bridged DOT in $237k Polkadot exploit

Hyperbridge, a cross-chain interoperability protocol built on Polkadot, suffered an exploit in which an attacker exploited a vulnerability in its gateway contract to mint 1 billion bridged DOT tokens on Ethereum and convert them into approximately $237,000.

How the exploit worked

Cybersecurity firm CertiK said the attacker introduced a forged message that enabled them to seize administrative control of the DOT token contract on Ethereum. With that access, the attacker minted the tokens in a single transaction and sold them immediately.

The rapid sell-off drove the price of bridged DOT from $1.22 to fractions of a cent. CertiK reported that limited liquidity in the bridged DOT pool constrained the attacker’s gains to 108.2 ETH, which it equated to the roughly $237,000 figure.

Likely technical root cause

Blockchain analytics firm Blocksec Falcon pointed to a replay vulnerability in Merkle Mountain Range (MMR) proofs as the likely underlying cause. It cited the absence of binding between the proof and its corresponding request, while noting that Hyperbridge has not officially confirmed this explanation.

Separately, a project contributor identified as Web3 Philosopher said the initial diagnosis suggested a malicious proof that deceived the protocol’s Merkle tree verifier.

Impact on markets and operations

The incident is notable because Hyperbridge marketed itself as a proof-based interoperability layer designed to provide “full node security” for cross-chain bridges. The exploit raised questions about that claim and added to a broader pattern of vulnerabilities affecting bridge infrastructure.

Polkadot said in a statement on X that the exploit affects only DOT bridged to Ethereum through Hyperbridge, with no impact on the native token or the wider Polkadot ecosystem. Even so, the price of native DOT fell nearly 4% to $1.18 before recovering slightly.

South Korean exchanges Upbit and Bithumb temporarily suspended deposits and withdrawals of the asset as a precaution.

Hyperbridge paused its operations while its team works on an update.

Broader context for DeFi exploits

The Hyperbridge incident follows another recent breach: protocol Aethir reported an exploit with losses below $90,000.

More broadly, global losses from exploits in the DeFi ecosystem during the first quarter of 2026 totaled $168 million, down from $1.58 billion in the same period of 2025.