THORChain loses about US$10.7 million after GG20 key leak; trading halted five weeks
THORChain, a cross-chain crypto swap network, lost about US$10.7M on 15 May 2026 when an attacker who joined as a node rebuilt a vault's key. Trading resumed 23 June. No funds confirmed returned. Nothing to update; users should treat any "refund" messages as scams.
Nothing to update: this was a theft from the network's vaults, not a flaw in an app on your device. If you hold funds in THORChain pools or synths, follow official THORChain announcements on how losses are shared, and ignore unsolicited refund or airdrop messages, which THORChain has warned are scams.
What’s happening
On 15 May 2026 an attacker drained about US$10.7 million from one of THORChain's five vaults. THORChain is a decentralised network for swapping crypto across blockchains. The attacker had joined as a node operator two days earlier. THORChain says a flaw in the GG20 threshold-signature scheme, which is meant to stop any one node holding a vault's key, leaked key material gradually, letting the attacker rebuild the full private key and sign withdrawals directly. The loss was first estimated at US$7.4 million, then revised. An automatic solvency checker halted trading on several chains, and node operators then halted the whole network. Law enforcement and Outrider Analytics were brought in. Trading resumed on 23 June 2026 after patches and checks of every vault and keyshare. As of the latest reports read, no stolen funds had been confirmed returned, and a bounty was on offer. Losses are to be covered under governance proposal ADR-028, using protocol-owned liquidity first. THORChain's blog lists later exploit reports from July and August, which were not read for this record. No arrests or attribution have been reported.
- What
- Breach
- Affects
- THORChain cross-chain crypto swap network
- Fixed in
- Nothing to patch
- Since
- 15 May 2026
- Closed
- 23 June 2026
Timeline
- All clearFixed
THORChain announced trading had resumed after about five weeks. Signing, churning, liquidity actions and swaps were live again, with every vault verified and every keyshare checked before restart.
- Update
Cointelegraph reported that no funds had been returned. THORChain had offered a bounty, planned to slash the attacker's node, and ADR-028 (still under node-operator vote) would take losses from protocol-owned liquidity first, then spread the remainder across synth holders.
- Update
THORChain published its first exploit report. It says the attacker rebuilt a vault's full private key through a flaw in the GG20 signing scheme it called progressive key material leakage. Law enforcement and Outrider Analytics were brought in, and the root-cause investigation was still going.
- New fixPartly fixed
THORChain said patch v3.18.1 was imminent, asked validators to scale down their Bifrost pods while it was finalised, and said recovery would be handled through governance proposal ADR-028, to be implemented in v3.19.
- Made publicNo fix yet
Unauthorised withdrawals drained one vault. The automatic solvency checker halted signing and trading on several chains about 52 minutes later, and node operators then voted to halt trading, signing, chain observation and churning. THORChain's first estimate of the loss was about US$7.4 million, revised to about US$10.7 million that evening.
- Update
A new node, bonded with about 635,000 RUNE, joined THORChain's active set and was assigned to one of the network's five vaults. A Discord user presumed to be the attacker had asked how to get a node churned in on 1 May.
Sources
- THORChain Exploit Report #1THORChain · 20 May 2026
- THORChain's $10M exploit: MPC vulnerability and private key leakCointelegraph · 22 May 2026
- THORChain resumes trading five weeks after $10.7 million exploitThe Block · 23 June 2026