出典確認済みリサーチ: OKX

What happened on 6 September

Blockstream's own incident assessment, published on 23 September and reposted on the Liquid blog on 25 September, lays out the sequence in detail.

At 13:53 UTC on 6 September, in Liquid block 4,050,336, an attacker submitted a transaction that created roughly 4,000 LBTC with nothing behind it. Liquid hides amounts with Confidential Transactions, and every confidential output carries a zero-knowledge rangeproof. To save work, the Elements software that runs Liquid caches the results of those expensive proof checks. A flaw in how the cache key was built let a new, invalid proof match an older entry that had already passed, so nodes holding that entry treated the forged output as verified without checking it again.

The attacker then pushed the unbacked LBTC through SideSwap, a Federation member that runs a peg-out service. At 14:28:56 UTC the Federation signers released 3,996.02 BTC on Bitcoin mainnet, and SideSwap forwarded almost all of it onward in the same Bitcoin block. Counting smaller peg-outs that were already in flight, the reserve fell from about 4,205 BTC to 197 BTC. Blockstream had the public bridge nodes taken offline at 18:26 UTC, which froze the sidechain.

Twelve minutes after that halt the attacker wrote on-chain that they were "whitehats" and asked for contact. After negotiation, 3,400 BTC was returned to the Federation peg wallet at 16:09 UTC on 7 September. Blockstream puts the remainder at approximately 602 BTC.

Why the bug existed, and why it was missed

The assessment describes two related defects. Bug A dates from an Elements change merged in May 2018 that dropped two fields from the rangeproof cache key. An outside researcher reported it on 2 August 2026, Blockstream patched its bridge nodes the next day, and 13 of the 15 functionary nodes had the fix by 11 August. The fix went into the public Elements repository on 1 September.

That narrower fix still joined the cache-key fields together without length markers, so two different inputs could produce the same byte string. That is Bug B, and it was exploited five days after the code became public. The researcher had in fact proposed a broader fix using length-prefixed serialization, but Blockstream's reviewers chose the smaller change for the production branch. Its corrective actions now make the structurally strongest fix the default for consensus-critical bugs and add an independent audit before such fixes ship.

The other failure was operational. SideSwap's peg-out key was not compromised, but according to the assessment SideSwap kept its signing key online, although the Federation charter calls for an offline receiving wallet, and it forwarded payouts automatically with no size limit or velocity check. A manually reviewed delay would have kept the released bitcoin recoverable.

Where recovery stands

Blockstream says it replayed the chain with the cache turned off, found two invalid outputs and four descendants, removed them, and verified that no inflated LBTC remains on the current chain. That matters: the problem today is not phantom coins circulating, it is a reserve that is short.

Crypto Briefing's 11 October report lists four conditions Liquid has attached to reopening peg-outs: full 1:1 BTC backing, further Elements upgrades, completed security audits, and changes to key management, including a move to cold storage. It also reports that Blockstream chief executive Adam Back has assured stakeholders the peg will ultimately be covered, without saying how.

The numbers, checked

Our arithmetic from the figures above: 197 BTC left after the drain plus 3,400 BTC returned gives about 3,597 BTC in the reserve. Add the 602 BTC still missing and full backing would be about 4,199 BTC, so the reserve covers roughly 3,597 ÷ 4,199 ≈ 85.7% of what it should. That matches the "about 86%" coverage cited in the reporting. At Binance's BTCUSDT price of $83,600 at 18:52 UTC on 11 October, the gap is worth about $50 million.

What it means if you hold L-BTC

• Your L-BTC is still a valid token on Liquid. You can send it, receive it and use it in Liquid applications. What you cannot do is redeem it through the peg for main-chain bitcoin.
• A token you cannot redeem trades on trust. Until the peg reopens, the value of L-BTC depends on the market's belief that the 602 BTC hole will be filled. If you need bitcoin now, the only route is selling L-BTC to another holder, at whatever price that holder offers.
• There is no first-come advantage to wait for. Liquid has said it will not reopen redemptions at partial coverage, which avoids a rush where the last people out are left short.
• Other Liquid assets are separate. Blockstream says USDt, DePix and other issued assets were unaffected by the exploit; they were only unavailable while the network was paused.
• Be wary of "help" messages. Blockstream warned users in September not to act on unsolicited messages claiming to come from Liquid or Blockstream. Recovery news is a classic phishing hook.

What to watch next

The next signals are an official Liquid or Blockstream statement on how the 602 BTC is being covered, the audit results, and a peg-out restart date. A staged restart with limits on withdrawal size would be consistent with the controls Blockstream says it is adding. The wider lesson echoes this week's other security news: Blockstream itself notes that AI-assisted tools are making old, quiet code easier to search for flaws, for defenders and attackers alike.

How to act on this

If you use Liquid only to move bitcoin cheaply between platforms, consider holding the bitcoin you may need soon on the main chain or at a venue where withdrawals are working, and keep sidechain or wrapped balances to an amount you could wait months to redeem. If you trade on a centralized exchange, check that it publishes proof of reserves and that BTC withdrawals are open before you deposit. OKX is one large venue that publishes proof-of-reserves reports; signing up with code nexu888 returns 40% of your trading fees, settled hourly (OKX profile). Our Ledger reseller analysis covers how to keep self-custody safe at the same time.

Quick answers

Can I withdraw L-BTC to bitcoin right now? No. Peg-outs have been disabled since 6 September and were still suspended on 11 October 2026.

How much bitcoin is missing from Liquid? About 602 BTC, according to Blockstream's assessment, after 3,400 BTC of the roughly 4,000 BTC taken was returned.

Was my L-BTC part of the hack? The inflated coins were created by the attacker and later removed from the chain. Ordinary holders' L-BTC remains on Liquid, but it cannot be redeemed until the reserve is whole.

Was Liquid USDt affected? No. Blockstream says USDt and other issued assets were unaffected, though they were unavailable while the network was paused.

When will peg-outs resume? No date has been announced. Liquid has tied the restart to full backing, software upgrades, audits and key-management changes.

Limits of this article

The technical sequence and reserve figures come from Blockstream's incident assessment and Liquid's public updates; the 11 October status, the restart conditions and Adam Back's assurance come from Crypto Briefing's report, which cites The Defiant, and we could not find a newer primary statement from Liquid. We did not verify the current secondary-market price of L-BTC. This is not investment advice. Partner links may earn NexuAlpha a commission paid by the exchange, at no extra cost to you.