{"investigation":{"slug":"liquid-network-blockstream","entity_name":"Liquid Network (Blockstream)","trust_score":28,"severity_base":null,"score_modifier":0,"confidence":0.82,"status":"draft","content_type":"investigation","summary":"Liquid Network is a Bitcoin sidechain operated by Blockstream and a federation of member exchanges, launched in 2018 to enable fast inter-exchange BTC settlement via a pegged asset called L-BTC. On September 6, 2026, attackers exploited a range-proof cache collision vulnerability in the underlying Elements software to mint approximately 4,000 unbacked L-BTC tokens and redeem them for roughly $320 million in real Bitcoin from the federation reserve, representing one of the largest crypto hacks of 2026. Attackers returned approximately 85% of funds after the vulnerability was patched, but retained roughly 598.5 BTC (~$47 million) as a self-declared bounty; Blockstream publicly rejected the bounty demand and characterized the retention as theft, not responsible disclosure.","sections":[{"content":"Liquid Network launched on September 27, 2018, as an inter-exchange settlement layer built by Blockstream on top of Bitcoin using the open-source Elements software. It allows participants to move BTC onto the sidechain as Liquid Bitcoin (L-BTC), a two-way pegged asset settled in approximately two minutes. The network is secured by a federation model: a quorum of geographically distributed member nodes holds the multisig keys that authorize BTC peg-ins and peg-outs. At launch, 23 founding member exchanges participated, including Bitfinex, BitMEX, OKCoin, Bitso, and others; membership later grew to approximately 87 entities across six continents. The standard peg-out authorization required 11-of-15 federation signatures. Confidential Transactions, a cryptographic privacy feature, concealed transaction amounts from non-parties but required range proofs to prove amounts were valid without revealing them.","heading":"Background and Network Architecture","sources":[{"url":"https://blockstream.com/press-releases/2018-10-10-blockstream-launches-the-liquid-network/","name":"Blockstream: Blockstream Launches the Liquid Network (press release, 2018)","type":"official","credibility":1},{"url":"https://help.blockstream.com/hc/en-us/articles/900003013143-What-is-the-Liquid-Federation","name":"Blockstream Help Center: What is the Liquid Federation?","type":"official","credibility":1}],"severity":"low"},{"content":"According to on-chain forensics reported by Bitquery, the exploit centered on a cache-collision vulnerability in the range proof verification logic of the Elements software. The cache key was constructed by concatenating four values — the proof, the hidden amount, the hidden asset, and the output script — and hashing the result, with no delimiters separating the fields. This design allowed two distinct input combinations to produce an identical hash key, meaning a proof previously cached for one set of values could be returned as valid for a fraudulent set. Between September 4 and September 6, 2026, the attacker conducted 92 preparatory test transactions and planted 68 identical range proofs in separate OP_RETURN outputs over approximately 14 hours (Liquid blocks 4,049,384 to 4,050,246), seeding the range proof cache across all federation nodes. At 13:53 UTC on September 6, the attacker minted approximately 4,000 L-BTC in Liquid block 4,050,336, backed by none of the required Bitcoin reserves. The attacker then submitted a peg-out request through SideSwap's peg-out service at 14:06 UTC. Because the peg-out request carried 11 valid federation signatures — meeting the standard 11-of-15 quorum — the federation's automated system processed it as legitimate and completed the 3,996 BTC payout in Bitcoin mainchain block 965,783 at 14:28 UTC. The entire exploit from mint to final payout took approximately 36 minutes. The Elements software fix, released as version 23.3.4 on September 9, 2026, introduced value-length prefixes in the cache key construction to prevent concatenation collisions.","heading":"September 2026 Exploit: Technical Details","sources":[{"url":"https://bitquery.io/investigations/liquid-network-hack-4000-btc-op-return","name":"Bitquery: Liquid Network Hack 4000 BTC OP_RETURN — Technical On-Chain Analysis","type":"on_chain","credibility":2},{"url":"https://www.trmlabs.com/resources/blog/2026s-biggest-hack-to-date-attackers-drained-usd-319-million-in-bitcoin-from-liquid-network-then-returned-85-of-funds","name":"TRM Labs: 2026's Biggest Hack — Attackers Drained $319 Million From Liquid Network","type":"research","credibility":2},{"url":"https://protos.com/how-4000-btc-walked-out-of-blockstreams-liquid-network/","name":"Protos: How 4000 BTC Walked Out of Blockstream's Liquid Network","type":"news_article","credibility":2}],"severity":"critical"},{"content":"At the time of the exploit, the Liquid federation reserve wallet held approximately 4,200 BTC. After the payout of approximately 3,996 BTC, the reserve fell to roughly 197 BTC — less than 5% of the BTC needed to back the approximately 4,205 L-BTC tokens outstanding at that moment. The Liquid.network dashboard reflected this under-collateralization in near real-time. Mempool.space flagged the event as an 'unauthorized -4019 BTC withdrawal.' The dollar value of the drained BTC was approximately $319-320 million at prevailing market prices on September 6, 2026, making this one of the largest single crypto hacks of 2026 by dollar value.","heading":"Scope of Funds Drained and Collateralization Impact","sources":[{"url":"https://www.trmlabs.com/resources/blog/2026s-biggest-hack-to-date-attackers-drained-usd-319-million-in-bitcoin-from-liquid-network-then-returned-85-of-funds","name":"TRM Labs: 2026's Biggest Hack — Attackers Drained $319 Million From Liquid Network","type":"research","credibility":2},{"url":"https://www.bloomberg.com/news/articles/2026-09-07/bitcoin-network-says-320-million-stolen-in-latest-crypto-hack","name":"Bloomberg: Bitcoin Network Says $320 Million Stolen in Latest Crypto Hack","type":"news_article","credibility":1}],"severity":"critical"},{"content":"Shortly after executing the withdrawal, the attackers embedded a message in a Bitcoin transaction OP_RETURN field reading 'we are whitehats. contact us on chain.' They subsequently communicated with the Blockstream team via encrypted on-chain messaging, and later shifted to unencrypted plaintext Bitcoin transactions — a move observers described as a deliberate publicity tactic. The attackers stated they would return the funds once the bug was patched and federation nodes were updated, framing their retention of approximately 598.5 BTC as compensation for discovering the vulnerability. In a later on-chain message, the attackers escalated to a demand that Blockstream pay an additional 10% bounty from company funds, warning: 'You SHALL pay 10% using your own money as bug bounty or you will cause all your holders a 15% loss for your irresponsibility and stinginess.' No formal bug-bounty agreement between Blockstream and the attackers has been publicly released. The attackers' self-identification as white hats is an unverified claim; no independent verification of their identity or prior authorization has been reported.","heading":"Attacker Communications and White Hat Claims","sources":[{"url":"https://gizmodo.com/white-hat-liquid-network-crypto-hackers-are-now-grandstanding-and-demanding-a-10-bounty-2000809413","name":"Gizmodo: White Hat Liquid Network Crypto Hackers Are Now Grandstanding and Demanding a 10% Bounty","type":"news_article","credibility":2},{"url":"https://therecord.media/liquid-network-blockstream-crypto-theft-hackers-keep-reward","name":"The Record: Liquid Network Blockstream Crypto Theft — Hackers Keep Reward","type":"news_article","credibility":2},{"url":"https://www.trmlabs.com/resources/blog/2026s-biggest-hack-to-date-attackers-drained-usd-319-million-in-bitcoin-from-liquid-network-then-returned-85-of-funds","name":"TRM Labs: 2026's Biggest Hack — Attackers Drained $319 Million From Liquid Network","type":"research","credibility":2}],"severity":"high"},{"content":"Security researchers and legal commentators widely disputed the attackers' characterization of their actions as responsible disclosure. Charles Guillemet, Chief Technology Officer of Ledger, stated the incident was 'straight extortion' and 'not how security work is done,' noting that proper disclosure would have involved contacting Blockstream's security team privately and allowing the company to pause operations and implement a fix before any funds were touched. Greg Sanders, a Bitcoin Core developer at Spiral, described the action as 'robbing a fancy bank, trying to keep a double digit percentage and accusing others of greed.' Legal analyst Vránová posted publicly that exploiting a vulnerability, taking 4,000 BTC, and demanding a fix as ransom constitutes extortion, potentially carrying felony charges and up to 20 years in prison under U.S. law, with additional computer-fraud charges. Pseudonymous analyst Shinobi observed that returning 100% of funds would have positioned the attackers for a substantial legitimate bounty 'completely in the legal clear,' but the demand transforms their conduct into publicly visible extortion. No law enforcement body has publicly confirmed a formal investigation as of this writing.","heading":"Expert Criticism of White Hat Framing","sources":[{"url":"https://gizmodo.com/hackers-drain-320-million-from-bitcoins-liquid-network-keep-47-million-for-themselves-in-white-hat-operation-2000808262","name":"Gizmodo: Hackers Drain $320 Million From Bitcoin's Liquid Network, Keep $47 Million in White Hat Operation","type":"news_article","credibility":2},{"url":"https://gizmodo.com/white-hat-liquid-network-crypto-hackers-are-now-grandstanding-and-demanding-a-10-bounty-2000809413","name":"Gizmodo: White Hat Liquid Network Crypto Hackers Are Now Grandstanding and Demanding a 10% Bounty","type":"news_article","credibility":2},{"url":"https://blockzeit.com/white-hats-face-backlash-from-47m-bill-in-liquid-network-exploit/","name":"Blockzeit: White Hats Face Backlash From Hefty $47M Bill in Liquid Network Exploit","type":"news_article","credibility":3}],"severity":"high"},{"content":"On September 7, 2026, approximately 3,400 BTC (roughly 85% of the drained funds, valued at approximately $270 million) was returned to the Liquid federation multisig address by the attackers at 16:09 UTC. The remaining approximately 598.5 BTC (~$47 million) was withheld by the attackers as their self-declared bounty. Blockstream deployed an emergency patch to its bridge nodes on September 7, 2026. The official Elements software fix — version 23.3.4 — was published on September 9, 2026, and included hardened range proof cache keys using value-length prefixes. Block production on Liquid Network resumed on September 10, 2026, at 12:26 UTC in a controlled mode, though peg-in and peg-out operations remained suspended while the network state was verified. Blockstream CEO Adam Back publicly pledged that the L-BTC to BTC one-to-one peg would be covered, urging L-BTC holders not to sell over-the-counter and stating the team was working through staged restoration of peg operations. Blockstream publicly rejected the attackers' 10% bounty demand on approximately September 11, 2026, characterizing the retention of funds as theft rather than responsible disclosure. As of this writing, no confirmed public report indicates all 598.5 BTC has been returned.","heading":"Fund Recovery and Network Restoration","sources":[{"url":"https://cryptobriefing.com/blockstream-liquid-network-exploit-funds-return/","name":"CryptoBriefing: Blockstream Confirms Bridge Nodes Patched, Funds Safe to Return After $320M Liquid Network Exploit","type":"news_article","credibility":2},{"url":"https://www.cryptotimes.io/2026/09/10/liquid-network-restarts-after-320m-exploit-adam-back-says-lbtc-peg-will-be-covered/","name":"CryptoTimes: Liquid Network Restarts After $320M Exploit — Adam Back Says LBTC Peg Will Be Covered","type":"news_article","credibility":2},{"url":"https://www.coindesk.com/markets/2026/09/08/white-hat-hackers-return-most-of-usd320m-bitcoin-taken-from-liquid-network","name":"CoinDesk: White Hat Hackers Return Most of $320M Bitcoin Taken From Liquid Network","type":"news_article","credibility":2},{"url":"https://www.bloomberg.com/news/articles/2026-09-08/bitcoin-s-latest-hack-puts-key-crypto-vulnerability-in-spotlight","name":"Bloomberg: Bitcoin's Latest Hack Puts Key Crypto Vulnerability in Spotlight","type":"news_article","credibility":1}],"severity":"high"},{"content":"The incident exposed structural risks in federated sidechain models. Although the 11-of-15 multisig design is intended to distribute trust across many parties, the shared use of a common software implementation — Elements — created a single, exploitable attack surface across all federation nodes simultaneously. The range proof cache was shared infrastructure, meaning no individual node's operational independence provided protection against a software-level exploit. Exchanges and market makers that rely on Liquid for inter-institution BTC settlement faced disruption when the network was paused and peg operations suspended. The incident has prompted broader discussion among researchers and practitioners about whether federated peg models can scale to the reserve sizes they attract without commensurate security auditing and formal verification of cryptographic primitives. Bloomberg noted the hack places 'key crypto vulnerability in spotlight' regarding Bitcoin sidechain infrastructure generally.","heading":"Systemic Risk: Federated Custody and Sidechain Infrastructure","sources":[{"url":"https://www.bloomberg.com/news/articles/2026-09-08/bitcoin-s-latest-hack-puts-key-crypto-vulnerability-in-spotlight","name":"Bloomberg: Bitcoin's Latest Hack Puts Key Crypto Vulnerability in Spotlight","type":"news_article","credibility":1},{"url":"https://finance.yahoo.com/markets/crypto/articles/320-million-hack-exposes-cracks-121936077.html","name":"Yahoo Finance: A $320 Million Hack Exposes the Cracks in Crypto's Plumbing","type":"news_article","credibility":2},{"url":"https://protos.com/how-4000-btc-walked-out-of-blockstreams-liquid-network/","name":"Protos: How 4000 BTC Walked Out of Blockstream's Liquid Network","type":"news_article","credibility":2}],"severity":"high"}],"timeline":[{"date":"2018-10-10","event":"Blockstream publicly announced Liquid Network.","source":"Blockstream press release","source_url":"https://blockstream.com/press-releases/2018-10-10-blockstream-launches-the-liquid-network/"},{"date":"2018-09-27","event":"Liquid blockchain went live at 1:29 UTC with 23 founding federation members.","source":"Blockstream press release","source_url":"https://blockstream.com/press-releases/2018-10-10-blockstream-launches-the-liquid-network/"},{"date":"2026-09-04","event":"Attackers began preparatory activity on the Liquid Network, conducting test transactions and seeding the range proof cache with 68 identical range proofs across 14 hours.","source":"Bitquery on-chain analysis","source_url":"https://bitquery.io/investigations/liquid-network-hack-4000-btc-op-return"},{"date":"2026-09-06","event":"At 13:53 UTC (Liquid block 4,050,336), attackers minted approximately 4,000 unbacked L-BTC by exploiting a range proof cache collision in the Elements software. At 14:28 UTC, the federation processed a 3,996 BTC peg-out via SideSwap, draining approximately $320 million from the reserve. The Liquid Network was paused and bridge nodes disabled. Attackers posted an OP_RETURN message: 'we are whitehats. contact us on chain.'","source":"TRM Labs, Bitquery, Bloomberg","source_url":"https://www.trmlabs.com/resources/blog/2026s-biggest-hack-to-date-attackers-drained-usd-319-million-in-bitcoin-from-liquid-network-then-returned-85-of-funds"},{"date":"2026-09-07","event":"Blockstream deployed an emergency patch to bridge nodes. Attackers returned approximately 3,400 BTC (~$270M, 85% of drained funds) to the federation multisig at 16:09 UTC. Approximately 598.5 BTC (~$47M) was withheld as a self-declared bounty.","source":"TRM Labs, CoinDesk, CryptoBriefing","source_url":"https://www.coindesk.com/markets/2026/09/08/white-hat-hackers-return-most-of-usd320m-bitcoin-taken-from-liquid-network"},{"date":"2026-09-08","event":"Security experts including Ledger CTO Charles Guillemet publicly rejected the white hat framing, characterizing the retained $47M as extortion. Bloomberg published analysis on systemic sidechain vulnerabilities exposed by the incident.","source":"Bloomberg, Gizmodo","source_url":"https://www.bloomberg.com/news/articles/2026-09-08/bitcoin-s-latest-hack-puts-key-crypto-vulnerability-in-spotlight"},{"date":"2026-09-09","event":"Elements software version 23.3.4 released with a patch hardening range proof cache keys against concatenation collisions.","source":"Bitquery on-chain analysis","source_url":"https://bitquery.io/investigations/liquid-network-hack-4000-btc-op-return"},{"date":"2026-09-10","event":"Liquid Network resumed block production at 12:26 UTC in a controlled mode. Peg-in and peg-out operations remained suspended. Blockstream CEO Adam Back publicly pledged that the L-BTC to BTC 1:1 peg would be maintained and covered.","source":"CryptoTimes, CryptoBriefing","source_url":"https://www.cryptotimes.io/2026/09/10/liquid-network-restarts-after-320m-exploit-adam-back-says-lbtc-peg-will-be-covered/"},{"date":"2026-09-11","event":"Blockstream publicly rejected the attackers' demand for a 10% bounty from company funds, characterizing the retention of 598.5 BTC as theft rather than responsible disclosure and stating 'We will not pay.'","source":"CryptoPotato, multiple outlets","source_url":"https://cryptopotato.com/we-will-not-pay-blockstream-rejects-10-bounty-demand-from-liquid-hackers/"}],"sources_used":[{"url":"https://www.bloomberg.com/news/articles/2026-09-07/bitcoin-network-says-320-million-stolen-in-latest-crypto-hack","name":"Bloomberg: Bitcoin Network Says $320 Million Stolen in Latest Crypto Hack","type":"news_article","archive_url":null,"credibility":1,"archive_timestamp":null},{"url":"https://www.bloomberg.com/news/articles/2026-09-08/bitcoin-s-latest-hack-puts-key-crypto-vulnerability-in-spotlight","name":"Bloomberg: Bitcoin's Latest Hack Puts Key Crypto Vulnerability in Spotlight","type":"news_article","archive_url":null,"credibility":1,"archive_timestamp":null},{"url":"https://www.coindesk.com/markets/2026/09/08/white-hat-hackers-return-most-of-usd320m-bitcoin-taken-from-liquid-network","name":"CoinDesk: White Hat Hackers Return Most of $320M Bitcoin Taken From Liquid Network","type":"news_article","archive_url":null,"credibility":2,"archive_timestamp":null},{"url":"https://www.coindesk.com/markets/2026/09/07/bitcoin-network-used-by-exchanges-hit-by-usd320-million-exploit-hackers-claim-they-re-the-good-guys","name":"CoinDesk: $320 Million Bitcoin Exploit Hits Liquid Network — Hackers Claim They Are the Good Guys","type":"news_article","archive_url":null,"credibility":2,"archive_timestamp":null},{"url":"https://therecord.media/liquid-network-blockstream-crypto-theft-hackers-keep-reward","name":"The Record: Liquid Network Blockstream Crypto Theft — Hackers Keep Reward","type":"news_article","archive_url":"http://web.archive.org/web/20260908194555/https://therecord.media/liquid-network-blockstream-crypto-theft-hackers-keep-reward","credibility":2,"archive_timestamp":"2026-09-08T19:45:55+00:00"},{"url":"https://www.trmlabs.com/resources/blog/2026s-biggest-hack-to-date-attackers-drained-usd-319-million-in-bitcoin-from-liquid-network-then-returned-85-of-funds","name":"TRM Labs: 2026's Biggest Hack — Attackers Drained $319 Million From Liquid Network Then Returned 85% of Funds","type":"research","archive_url":"https://web.archive.org/web/20260911164023/https://www.trmlabs.com/resources/blog/2026s-biggest-hack-to-date-attackers-drained-usd-319-million-in-bitcoin-from-liquid-network-then-returned-85-of-funds","credibility":2,"archive_timestamp":"2026-09-11T16:40:23+00:00"},{"url":"https://bitquery.io/investigations/liquid-network-hack-4000-btc-op-return","name":"Bitquery: Liquid Network Hack 4000 BTC OP_RETURN — On-Chain Investigation","type":"on_chain","archive_url":"https://web.archive.org/web/20260911162317/https://bitquery.io/investigations/liquid-network-hack-4000-btc-op-return","credibility":2,"archive_timestamp":"2026-09-11T16:23:17+00:00"},{"url":"https://protos.com/how-4000-btc-walked-out-of-blockstreams-liquid-network/","name":"Protos: How 4000 BTC Walked Out of Blockstream's Liquid 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a 10% Bounty","type":"news_article","archive_url":"http://web.archive.org/web/20260910153059/https://gizmodo.com/white-hat-liquid-network-crypto-hackers-are-now-grandstanding-and-demanding-a-10-bounty-2000809413","credibility":2,"archive_timestamp":"2026-09-10T15:30:59+00:00"},{"url":"https://www.cryptotimes.io/2026/09/10/liquid-network-restarts-after-320m-exploit-adam-back-says-lbtc-peg-will-be-covered/","name":"CryptoTimes: Liquid Network Restarts After $320M Exploit — Adam Back Says LBTC Peg Will Be Covered","type":"news_article","archive_url":null,"credibility":2,"archive_timestamp":null},{"url":"https://cryptobriefing.com/blockstream-liquid-network-exploit-funds-return/","name":"CryptoBriefing: Blockstream Confirms Bridge Nodes Patched, Funds Safe to Return After $320M Liquid Network 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