LND v0.21 fix protects channels; older nodes risk full loss

LND nodes running versions earlier than v0.21.0 can lose an entire Lightning channel balance if a counterparty triggers a one-block Bitcoin reorganization and then publishes a revoked commitment transaction after a cooperative close. Reproduced tests showed the condition can yield a maximum-loss outcome for the channel. According to researcher Bastien Teinturier, no users were known to be affected in the wild.

The issue arose because LND considered a cooperatively closed channel resolved after the closing transaction received a single confirmation. Once LND removed the in-memory and on-disk channel state at that point, the node lacked the data needed to detect a later reorganization and to publish the penalty transactions required when an old, revoked commitment appears on-chain.

The corrective code was merged into the project’s master branch on Jan. 16, 2026 as pull request #10331 and associated with the 0.21.0 release line. A backport to the 0.20.x branch was reverted and subsequent documentation and release notes indicate the reorganization-safe close logic landed in 0.21.0. As of Aug. 25 the project’s latest official package was v0.21.2-beta, published Aug. 13.

The patched behavior retains the channel’s close state until multiple confirmations are observed and subscribes to reorganization notifications so the node can still publish penalty transactions if a revoked commitment appears. Exploitation requires three conditions to align: a cooperative close that the honest node has seen at least one confirmation for, a one-block reorganization that removes that confirmation, and a malicious counterparty that possesses and publishes a previously revoked commitment.

Operators running standard LND releases older than v0.21.0 should assume they lack the official reorg-safe close logic unless they have applied an independent patch. Project guidance recommends running the latest minor release of the newest major version an operator can support to ensure these and other fixes are present.