Bitcoin Core discloses low-severity undo file overflow bug and releases fixes

What sources claim

• The project said a miner can produce valid blocks whose undo data is much larger than the blocks themselves, enough to push a single undo file past 4 GiB, and that exploiting this on 64-bit systems is impractical, requiring several thousand blocks of nonstandard transactions, roughly a month of the entire network's block production.
• Bitcoin Core said a fix for 64-bit systems was released in versions 29.5, 30.4, 31.2 and 32.1, storing block and undo file positions as 64-bit integers while leaving the on-disk format unchanged.
• The project said 32-bit systems remain affected because their positioning calls are limited to 2 GiB, and nodes whose blocks directory is on FAT32 remain affected because that file system caps files at 4 GiB.

Still unresolved

• Whether any node has actually shut down from this bug, and whether an official statement or on-chain data would confirm exploitation, is not stated.
• When patched releases for 32-bit systems or FAT32 storage will be issued is not specified.

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