Bitcoin Core developers alerted users about a significant bug in versions 30.0 and 30.1 that could lead to wallet file deletions and subsequent fund losses. The flaw specifically affects older wallet migrations that have not been renamed or upgraded.

The bug manifests when the software attempts to migrate a legacy “wallet.dat” file located in a custom wallet directory defined by the “-walletdir” setting, particularly with pruning enabled. Users who don’t have an external backup risk losing access to all of their local wallet files.

Lacie Zhang, a market analyst at Bitget Wallet, commented that this issue can lead to guaranteed fund loss if the conditions are met. Shawn Odonaghue from Orbs echoed these sentiments, emphasizing that only very old wallet setups are at risk. Users equipped with hardware wallets or modern software are unlikely to face these issues.

Related: Bitcoin Core Secures Praise After Audit Finds No Serious Flaws

Immediate Action by Bitcoin Core

Following the disclosure of this vulnerability on January 1, 2026, Bitcoin Core has removed versions 30.0 and 30.1 from their download site. The community is advised against using the wallet-migration tools until a fix is released, while existing node operators can continue their usual operations without issue.

Bitcoin trackers such as Coin Dance indicate that Bitcoin Core dominates with approximately 78% of reachable Bitcoin nodes. This degree of concentration means that even a minor bug in its operation can have expansive repercussions for the ecosystem.

Zhang mentioned that the bug, although not critical to the consensus, still illustrates the broader risk when one implementation is widely used.