CVE-2025-62861

Name of the Vulnerable Software and Affected Versions Bitcoin Core versions 28.0 through 28.2 Bitcoin Core versions 29.0 through 29.1

Description A high-severity issue exists where a mining node may become unable to produce valid block templates following a chain reorganization (reorg), a process where a node switches to a competing chain with more accumulated work. This occurs due to a flaw in the sibling eviction logic related to Topologically Restricted Until Confirmation (TRUC) transactions (version 3 transactions defined in BIP 431). TRUC transactions are subject to mempool policy rules that limit how unconfirmed transactions can chain together to prevent pinning attacks, where a time-sensitive transaction is blocked from being sped up with a higher fee.

During a reorg, transactions from displaced blocks are re-added to the mempool. Because the bypass limits path was not properly gated, the sibling eviction mechanism could mistakenly remove a restored transaction while leaving its descendants in the mempool. This creates an inconsistent state where descendants spend outputs that no longer exist, causing the block template validity check to fail. Affected nodes must be restarted to reload the mempool and restore consistency. Approximately 9% of reachable nodes were reported to be running affected versions.

Recommendations Update Bitcoin Core versions 28.0 through 28.2 to version 28.3. Update Bitcoin Core versions 29.0 through 29.1 to version 29.2. As a temporary workaround, restart the affected node to clear the error state and restore the ability to produce block templates.