Critical wallet bug found in Bitcoin Core v30, users urged to backup

• Legacy wallets risk deletion during Bitcoin Core v30 migration.
• Back up wallet and data directories before attempting upgrades.
• Modern wallets and hardware wallets remain largely safe.

A critical bug has been discovered in Bitcoin Core v30, raising alarms for users planning to upgrade their wallets.

The issue specifically affects the wallet migration process, which is designed to transfer old wallets to the latest software version.

Under certain conditions, this migration can delete wallet files, putting users’ funds at risk.

Developers have confirmed that the bug primarily impacts older legacy wallets, particularly those that have not been renamed or updated in years.

Modern wallets and hardware wallets are largely unaffected, according to official sources.

However, the risk remains significant for anyone running a node with outdated wallet files and attempting a migration.

The Bitcoin Core wallet bug

The problem arises when Bitcoin Core tries to migrate an unnamed legacy wallet located in a custom wallet directory.

If pruning is enabled, the software can misinterpret the migration process and inadvertently delete all files in the wallet directory.

This is not a network-level bug, so the Bitcoin blockchain itself remains secure.

Instead, the threat is local: users may lose access to their funds if no external backup exists.

The vulnerability only triggers during migration attempts.

Simply running the software or syncing the blockchain is not enough to cause file deletion.

Developers quickly responded by removing v30.0 and v30.1 binaries from the official download page.

Users are now urged to avoid running any wallet migrations until a fixed version is released.

Steps users should take

The Bitcoin Core v30 bug is dangerous but avoidable, provided users follow official guidance and prioritise backups.

Bitcoin Core recommends backing up the entire wallet and data directories before attempting any upgrades.

This precaution can prevent potential loss, especially for legacy wallet users.

It is also advised to check whether the wallet is classified as “legacy” or “modern.”

For those with legacy setups, extra care should be taken when handling migration procedures.

Users should also verify their directory configurations, including the -walletdir parameter, to ensure files are not accidentally removed.

Keeping offline or external backups remains the safest way to protect funds.

While the bug does not compromise the network, the risk to individual wallets is real and immediate.

The community is awaiting the release of Bitcoin Core v30.2, which will address the migration bug and restore safe upgrade procedures.

Until then, cautious users are strongly advised to pause any wallet migrations and secure backups externally.

The discovery of this bug serves as a reminder that software updates, while necessary for security and performance, can introduce unforeseen risks to legacy systems.

By taking simple precautions, users can avoid potential losses and ensure their Bitcoin holdings remain safe.

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