Bitcoin Core's Disk Fill Bug: Finally Squashed?

Bitcoin Core developers appear to have finally exterminated the pesky disk fill attack that has bothered full node operators since 2020.

Bitcoin Core developers have been battling a persistent disk fill attack since 2020. The latest news suggests they may have finally squashed it! This blog post dives into the details of this long-standing issue and the potential fix.

The Disk Fill Attack: A Nuisance for Full Nodes

The disk fill attack is a real headache for those operating full Bitcoin nodes. Attackers exploit commands like LogPrintf to flood the node's hard drive with excessive, pointless data. For older nodes with spinning disks, this can be crippling, filling up their storage with garbage.

Even flash storage isn't immune. The constant writing can degrade the disk and even cause the entire machine to crash. It's like being forced to write the same sentence over and over until your hand cramps up and falls off.

The Extermination Attempt: A Five-Year Saga

Bitcoin Core Pull Request (PR) 32604, a revival of several earlier attempts, represents the culmination of five years of work. Senior Bitcoin Core developer Gloria Zhao merged bug patch 2d59977 into the master branch. The commit passed all checks with no negative acknowledgements from other developers.

Bitcoin Core Version 30: Expanding OP_RETURN

In other news, Bitcoin Core's upcoming version 30 (slated for October 2025) will dramatically raise the OP_RETURN data limit—from 80 bytes to nearly 4 MB. This change permits developers to put more rich metadata on-chain. While proponents argue this enables more complex, data-driven Bitcoin applications, critics express concern that it could bloat the blockchain and negatively impact decentralization. It's a bit of a trade-off, but could open new doors for Bitcoin use.

The Future: Hopeful, but Vigilant

The hope is that with the next Bitcoin Core release, this patch will spread across the network and finally put an end to the disk fill attack. As a voluntary software package, full node operators need to manually upgrade to benefit from the fix.

Currently, around 16% of node operators are running version 29.0. Adoption of the latest version is key to fully mitigating the attack. So, if you're running a full node, it might be time to consider an upgrade.

So, fingers crossed, this pesky bug is finally gone for good. But in the world of Bitcoin, you can never be too sure. Keep your nodes updated, and stay vigilant!