Bitcoin Core developers uncover critical wallet migration bug in versions 30.0 and 30.1

Bitcoin Core developers publicly revealed they found a critical bug in versions 30.0 and 30.1 of the software, an issue that affects the wallet migration process from legacy wallets to what they called modern descriptor wallets. 

According to an X post shared by the developers, the wallet migration bug was found in Bitcoin Core wallet versions 30.0 & 30.1.

They also revealed that under rare circumstances, migrating a legacy (BDB) wallet can potentially end in the deletion of all wallet files on the same node, and if those wallets aren’t backed up, they say it can result in a loss of funds.

Is there a bug in the Bitcoin Core wallet? 

In a statement shared on their website, the Bitcoin Core developers claim that the bug is triggered only during attempts to migrate the legacy wallet, as it requires the presence of a default (unnamed) wallet.dat file, which was released five years ago and has not been created by default since 0.21, and fails to be migrated or loaded. 

They added that a condition that could trigger this is when pruning is enabled, and the wallet is unloaded while pruning is in progress.

The developers have promised that a fix will become available in Bitcoin Core 30.2, but out of an abundance of caution, they got rid of the binaries for affected releases from bitcoincore.org.

However, until the fixed version becomes available, users have been urged to avoid migrating their legacy wallets using versions 30.0 or 30.1, the GUI or RPC, until v30.2 is released.

They have also claimed that only the legacy wallet migration process was affected as a result of the bug. “You can continue using Bitcoin Core normally, including existing wallets and running a node without wallets,” the post concluded. 

According to Lacie Zhang, market analyst at Bitget Wallet, technically proficient users can assess their exposure to the bug by checking which version of Bitcoin Core they are running to determine whether their wallet is a legacy wallet. 

They can also inspect their respective “debug.log” to see whether pruning is enabled and whether any migration attempts have already occurred, and by reviewing the directory layout to confirm whether “-walletdir” points to a custom or mounted location.

“Risk is highest if all these conditions are present and a migration has either been attempted or is pending,” she said. “If no migration has occurred yet, users should immediately back up the entire data directory to external media and avoid restarting or upgrading until moving to version 30.2 or later.”

Response to the announcement has been hostile 

The Bitcoin Core developers have acknowledged the bug and are deploying control measures in what many consider a professionally coordinated response. However, Crypto Twitter has unloaded in typical fashion, with many highlighting how low the platform has sunk. 

Some just dropped discouraging commentary, while others tried to recruit others to join them in dumping the platform for a better alternative. 

The ire from the Bitcoin Core community comes after Core v30 caused what is being referred to as a minor civil war among developers who disagreed over easements to arbitrary data storage on Bitcoin’s blockchain, claiming it turned BTC into a data dump. 

Before it was finally released, it was heavily reviewed and saw a delay that lasted weeks, only for it to come out with a serious bug.

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