Cross-Chain Bridge Hacks: A History, and How to Lower Your Risk

Short answer

Many cross-chain services have been hacked, and a clean record doesn't prove a service is safe. THORChain reported exploits in 2021 and 2026, LI.FI in 2022 and 2024, and Chainflip in 2026; deBridge reported a failed attempt in 2022. In August 2022, Chainalysis estimated that $2 billion had been stolen in 13 bridge hacks, and that bridge attacks made up 69% of all crypto stolen so far that year (Chainalysis).

Most of the incidents below (10 of 13) came from stolen or compromised keys, broken message checks, flaws in contracts holding open approvals, or signing and payout flaws.

You can't remove the risk, but approving exact amounts and revoking old approvals shrink it; a small test transfer limits what a mistake costs.

SwapBee publishes this guide. Two of the projects below, LI.FI and Bungee (Socket), are SwapBee providers.

Why are bridges a target?

Bridge designs vary, but a common one holds a large pool of coins on one chain and issues matching coins on another when it receives a valid message. Anyone who can forge that message, or steal the keys that sign it, can empty the pool. Pools can be large: Nomad's fell from $190,740,000 to $1,794 in a few hours (Halborn).

Which cross-chain services have reported hacks?

Sources checked on 7 October 2026; archive copies are dated where cited.

What went wrong in these hacks?

1. Stolen or compromised keys

Many bridges let a small group of validators approve withdrawals; with enough of their keys, attackers can sign any withdrawal.

• Ronin: attackers obtained keys to five of the nine validators. Malwarebytes, citing The Block, and OnChainAttack say it began with a fake job offer (Malwarebytes, OnChainAttack). In April 2022, the FBI tied Lazarus Group to the "$620 million in Ethereum" theft reported on 29 March, which OnChainAttack identifies as Ronin (FBI, OnChainAttack).
• Harmony Horizon: Harmony said the attackers compromised at least two of the four private keys of its bridge validators (Harmony). In January 2023, the FBI named Lazarus Group for this theft too.
• Multichain: Chainalysis reported that the team said it lost the platform's keys after its CEO's arrest, and that the hack appears to have been "the result of keys being compromised"; it is not clear who made the withdrawals (Chainalysis).

2. Bugs in message checks

A bridge must check that each message from the other chain is genuine.

• Wormhole: a flaw in signature checks let an attacker mint 120,000 wrapped ETH on Solana with no ETH behind them. Jump Crypto later refilled the contract with 120,000 ETH (Wormhole, as archived 28 August 2026).
• Nomad: a contract upgrade on 21 June 2022 let unproven messages pass the check, so anyone could forge one (Nomad, as archived 30 September 2026). In all, hundreds of wallets joined in, across 960 transactions (Halborn).

3. Open token approvals

Some token swaps require a contract approval. An unlimited approval can remain active until you revoke it.

At LI.FI in March 2022 and July 2024, and at Socket, which Bungee's docs now describe, in January 2024, a flaw in new contract code let attackers drain wallets with unlimited approvals.

4. Signing and payout flaws

Networks that hold native coins in vaults on many chains, such as THORChain and Chainflip, can also fail in their signing or payout systems, not only in contracts.

• THORChain, May 2026: a node that had joined two days earlier used a mix of three small flaws in the signing library to rebuild one vault's private key (THORChain report #2).
• Chainflip, September 2026: an attacker got six withdrawals from its Tron vault paid out twice. Its validators later voted to repay affected liquidity providers from vault surplus (Chainflip).

Does "never been hacked" mean a service is safe?

If you're looking for a service that has never been hacked, a clean record is worth something, but it is not proof of safety. LI.FI's and Socket's 2024 losses both came from newly added code. THORChain says its 2026 loss came from long-present flaws in a signing library inherited from Binance, which Binance had since fixed.

Some attempts fail. In August 2022, deBridge's co-founder said the team had been targeted with a spoofed email that he said was apparently from the Lazarus group (Decrypt). A better question is how a team responds: does it pause, explain and repay users?

How can I lower my risk?

1. Don't hold wrapped tokens longer than you need to. They are only as good as the bridge holding the real coins; Wormhole's wrapped ETH was not fully backed until Jump Crypto recapitalised the contract.
2. Approve exact amounts where your wallet allows it.
3. Revoke old approvals. Tools such as Revoke.cash list them for you.
4. Test with a small amount first on a new route or chain; a small success doesn't prove the route is secure.
5. If you split a large transfer, wait for each part to arrive before sending the next.

How does SwapBee handle cross-chain swaps?

On SwapBee you send coins from your own wallet to a deposit address made for your swap, with no account and no wallet connection, and the new coins go to an address you choose. There are no accounts, balances or pooled wallets: most swaps send your deposit straight to the provider, and on-chain DEX swaps use a one-time swap address SwapBee operates, which executes the swap and sends the output to your wallet automatically. Before you confirm, each quote's provider policy shows who holds your deposit; that holder's security matters. The provider may ask for checks, and in exceptional cases SwapBee may ask for information (AML policy).

Many routes go through exchange services that deliver the coin you chose; others use cross-chain aggregators such as LI.FI and Bungee. Each quote names its provider, so you can check its record first. See how cross-chain swaps work on SwapBee or our comparison of cross-chain swap aggregators.

FAQ

What was the biggest bridge hack?

Of the table's incidents with a dollar figure, the two largest at the time were Poly Network in August 2021 ($610 million in assets affected, not counting $33 million in frozen USDT, which Poly Network said it regained control of) and Ronin in March 2022 (about $600 million to $625 million).

Are cross-chain swaps safe?

No route is free of risk. In August 2022, Chainalysis wrote that bridges often keep funds in one central place, which makes them a target, and that effective bridge design was still an unresolved technical challenge (Chainalysis). The incidents in this guide involved keys, message checks, approvals and signing, so check what your route relies on.

Do I need to revoke approvals after a swap?

If you gave an unlimited approval, revoke it when you're done: it stays open until you do, and attackers have used open approvals before.

Has THORChain been hacked?

Yes. THORChain reported two exploits on its Ethereum router in July 2021, and on 15 May 2026 an attacker combined three small flaws in its signing library to drain about $10 million to $10.7 million, by THORChain's reports #1 and #2, from one of its five vaults.

Popular cross-chain swaps: BTC to ETH, BTC to SOL, ETH to SOL, USDT (Tron) to USDT (Ethereum).

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