Liquid Network incident, 2026-09-06

Liquid hides amounts with Confidential Transactions: each output carries a commitment plus a rangeproof showing the hidden value is non-negative. Without that proof, commitments can balance a huge positive output against a negative one — that is, create coins. Because proofs are expensive to check, Elements caches successful verifications. The cache key did not unambiguously bind all the data the proof depends on (value commitment, asset commitment, script), so two different inputs could map to the same cache entry (CertiK). The attacker first got a legitimate proof verified and cached, then submitted an inflating output that hit the same entry and skipped verification (Chainalysis).

The peg-out side then behaved as designed: it trusts the sidechain's validated state and has no separate reserve check, so a consensus-level inflation becomes a real BTC withdrawal (Blockstream). That is the uncomfortable lesson for federated pegs: a well-run federation does not help if every member runs the same software with the same bug. A per-peg-out sanity check against total issued supply, or rate limits on peg-out size relative to reserves, would have bounded the loss.

For comparison with the bridges we track: intent bridges such as Across or Relay hold far smaller pools and settle each fill separately, so a single forged mint cannot drain years of deposits in minutes. A federated peg concentrates the whole reserve behind one validation rule, which is efficient in normal times and catastrophic when that rule fails.

At the time

L-BTC holders could not act during the halt: peg-outs were frozen and the gap between L-BTC supply and BTC reserves was not something an individual could hedge in time. The practical step was to avoid buying discounted L-BTC on secondary markets until Blockstream published reserve figures.

Now

Treat any wrapped or pegged BTC as carrying the risk of its issuer's software and signers, not Bitcoin's. Check whether the issuer publishes live reserves, and keep large balances in native BTC between uses. For cross-chain BTC routes, our route pages show which bridges quote them and how; none of the bridges we track use Liquid.