Blockstream's Liquid Network Halts After 4,000 Bitcoin Leaves Through an Approved Peg-Out
At 14:28 UTC on Sunday, the Liquid Federation paid out 3,996 bitcoin to a customer’s address on the main chain. Nothing about the payment looked wrong. A peg-out request had come in through SideSwap, an approved trading venue on the network, the matching L-BTC had been burned on the sidechain the way the protocol requires, and the signers signed. A small 2.5 BTC transfer had gone out just before it. The two amounts ended up consolidated in a single address holding about 3,998.5 BTC.
Then a message showed up on chain: “we are whitehats. contact us on chain.”
The federation wallet that backs L-BTC held roughly 4,200 BTC before this. It now holds a bit over 200. At current prices the missing coins are worth around $320 million, which makes this one of the larger single-day drains of the year, and by some distance the largest ever to hit a Bitcoin sidechain.
Liquid disabled its bridge nodes and halted new transactions. The chain itself keeps producing blocks. Exchanges were told to pause L-BTC deposits and withdrawals, and most of them have. Other assets issued on Liquid, including USDT, DePix and the tokenized real-world assets that several Brazilian issuers run there, were not touched.
The Keys Were Fine
The detail that separates this from the usual crypto incident is that nobody stole a key.
Liquid’s reserve sits in a multisig held by fifteen known corporate functionaries, with eleven signatures needed to move anything. That design exists to stop exactly the kind of loss that just happened, and it worked. Blockstream says the peg-out used a valid SideSwap peg-out authorization key, and that it has found no evidence the key was compromised.
What went wrong sits a layer below. Blockstream traced the incident to a bug in Elements, the software Liquid runs on, which had allowed L-BTC to be created that no locked bitcoin was standing behind. SideSwap had no way of telling the bug-created L-BTC from the real kind, because on the ledger they looked identical, so it processed the peg-out request the way it processes every other one. The federation then honored a claim the protocol considered legitimate. Everything downstream of the bug behaved correctly, which is precisely why the money left so smoothly.
Security researchers put the flaw at the node level in Liquid’s transaction handling. Samson Mow, whose JAN3 builds the Aqua wallet, suggested early on that Confidential Transactions may be involved, though the developers have not confirmed that. Confidential Transactions hide amounts behind cryptographic commitments, and the whole point of the scheme is that the network can verify that inputs balance outputs without seeing either. If the verification of that balance can be tricked, an attacker mints value out of nothing and nobody watching the chain sees a thing. That is the inflation-bug shape, and it is the worst class of failure a confidential ledger can have.
The White Hat Question
The people holding the coins have said they will send most of them back once the Elements vulnerability is patched and every node on the network is running the fix. They also sent Blockstream encrypted technical details of what they found, according to Galaxy’s Alex Thorn. Blockstream has been answering through signed OP_RETURN messages on the Bitcoin chain, starting with a request that they get in touch by email.
Not everyone is buying the framing. Charles Guillemet, Ledger’s CTO, pointed out that asking to be contacted on Signal is not how disclosure normally works. Mow noted something sharper: the message asking Blockstream to move the conversation to Signal did not come from the address holding the 4,000 BTC, so somebody unconnected to the exploit was trying to insert themselves into the negotiation. Moving nine figures first and announcing good intentions afterward is leverage, whatever it gets called. The coins have not moved since.
What Is Actually Stuck
Everyone holding L-BTC right now has a claim on a reserve that no longer covers it. About 207 BTC sits behind an outstanding supply that was issued against roughly twenty times that. Wallets with Liquid features are showing balances their users cannot redeem; Aqua’s Liquid side is affected, its on-chain bitcoin side is not. Until the coins come back or the federation finds another way to make holders whole, the peg is a promise rather than a reserve.
Liquid was built in 2018 to solve a narrow problem for exchanges, which is that Bitcoin settlement is slow and public. Lock BTC with a federation, issue L-BTC against it, move value between venues in a minute with the amounts hidden. More than eighty exchanges, infrastructure firms and asset managers signed on to the federation. The trust assumption was always explicit and people accepted it, because the alternative was waiting for confirmations.
That assumption turns out to have been narrower than advertised. Participants were asked to trust that eleven of fifteen named institutions would not collude and would not lose their keys, and that held up perfectly. What they were also trusting, without much discussion, was the correctness of the code that decides what a valid coin is. There is no quorum of reputable signers that protects against a validity bug, because the signers are doing what the software tells them is right.
Every bridge and every sidechain in production carries the same unpriced risk. The industry has spent years hardening custody, adding signers, distributing keys, and moving hardware into vaults, all of it aimed at the theft model where somebody gets access they should not have. This one came in through the front door with valid paperwork.
Liquid has not said when it will reopen.