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Lightning Labs warns of bug that can mark canceled Lightning invoices paid

Lightning Labs said a mismatch between invoice records and network outcomes can cause a merchant to release goods or provide credit without receiving funds, though it gave no tally of losses.

Reported · Written up by our desk · Market Structure

Lightning Labs disclosed on Sept. 21, 2026 that a flaw in older Lightning Terminal software could record a Bitcoin Lightning invoice as paid even after the payment was cancelled and returned to its sender. The company warned that a merchant relying on that status could release goods or issue credit without receiving funds, and it did not provide a tally of actual merchant losses.

The issue stems from a mismatch between the software invoice record and the payment outcome. Lightning Labs said the Lightning payment uses a hashed time-locked contract, or HTLC, and in this case the HTLC was cancelled on the network and returned to the sender while the receiving node still recorded the invoice as settled.

Lightning Terminal bundles tapd, software for Taproot Assets, with the lnd Lightning node. Lightning Labs said that in the affected setup, tapd treated any HTLC carrying custom wire records as an asset payment, and a trigger that included an experimental endorsement record even for ordinary BTC payments led tapd’s strict-forwarding rule to instruct lnd to cancel the HTLC.

CryptoSlate reported the advisory does not describe a failure of Bitcoin’s base chain, and Lightning Labs said the trigger did not require the merchant to have any specific action, based on the advisory details provided.

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