Lightning Labs reveals bug allowing canceled invoices to appear paid

A flaw in older Lightning Terminal software could incorrectly mark a Bitcoin Lightning invoice as paid after the payment was canceled and returned to the sender, Lightning Labs disclosed on Sept. 21, 2026. Merchants relying on this status could release goods or credit without receiving funds, although no actual merchant losses were reported. The issue arose from a mismatch between the software's invoice record and the payment outcome, where a canceled HTLC was still recorded as settled. Lightning Terminal bundles tapd software with the lnd Lightning node, and in the affected setup, tapd treated HTLCs with custom wire records as asset payments. Some sender implementations added experimental endorsement records to ordinary BTC payments, leading to the cancellation of the HTLC set without requiring open asset channels. Additionally, a defect in lnd caused invoices to be marked as settled even after the HTLC was canceled. Lightning Labs rated the vulnerability as high severity due to the risk of releasing value against incomplete payments, although sender funds were not at risk. Fixes for both defects were included in Lightning Terminal v0.15.0-alpha, with earlier versions affected. The tapd trigger was fixed in v0.5.1 on Feb. 12, 2025, and lnd v0.19.0-beta addressed the accounting error on May 22, 2025. The advisory highlighted a vulnerability that had been resolved in 2025.

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