Bitcoin Core developers warned users on Monday about a wallet migration bug in versions 30.0 and 30.1 that could delete wallet files and result in a loss of funds.
The issue occurs under specific conditions and affects migrations from older Bitcoin Core wallets that were never renamed or previously upgraded.
Lacie Zhang, a market analyst at Bitget Wallet, told Cointelegraph that the bug is triggered when the software attempts to migrate an unnamed legacy wallet.dat file stored in a custom wallet directory — often set using the -walletdir option — while pruning is enabled.
In such cases, the migration may appear to complete successfully, but a flaw in the cleanup process can mistakenly delete the entire wallet directory. Without an external backup, users could permanently lose access to their funds, as all local wallet files are removed.
Shawn Odonaghue, community lead at layer-3 blockchain Orbs, said the issue primarily affects “very old wallet setups,” adding that users relying on hardware wallets or modern wallet software are unlikely to be impacted.
Bitcoin Core pulls binaries and prepares fix
Bitcoin Core version 30.1 was released on Jan. 1, and the wallet migration bug was publicly disclosed on Monday. In response, developers removed the 30.0 and 30.1 binaries from the official download site as they work on a fix.
The Bitcoin Core project advised users to avoid using the wallet migration tools until a fixed release, Bitcoin Core 30.2, becomes available. Developers emphasized that users who are not attempting wallet migrations can continue running their nodes as normal.
Zhang added that technically proficient users can evaluate their exposure by confirming whether they are running Bitcoin Core versions 30.0 or 30.1, determining if their wallet is a legacy setup, and reviewing the debug.log file to see whether pruning is enabled and whether any migration attempts have already occurred. Users should also inspect their directory structure to verify whether the -walletdir parameter points to a custom or mounted location.
“Risk is highest if all of these conditions are present and a migration has either been attempted or is pending,” Zhang said. “If no migration has occurred yet, users should immediately back up the entire data directory to external storage and avoid restarting or upgrading until moving to version 30.2 or later.”
Bitcoin Core dominates node software
According to Bitcoin data tracker Coin Dance, Bitcoin Core currently powers around 78% of reachable Bitcoin nodes. Alternative implementations such as Bitcoin Knots account for nearly 22% of the network.
That level of dominance means even narrowly scoped wallet bugs can have implications for the broader ecosystem.
“The bigger takeaway is concentration risk,” said Odonaghue. “Bitcoin Core holds a massive share of the ecosystem, and there are few truly mainstream alternatives. When a single implementation becomes the default, any bug or design decision can have an outsized impact.”
Zhang added that while the issue was not “consensus-critical,” it highlights how problems at the wallet layer can still scale into ecosystem-wide risks when one implementation dominates usage.
