# CVE-2026-117346: Bitcoin Core denial of service via unbounded undo files

Source: https://junglewise.ai/threats/cve-2026-117346-bitcoin-core-through-31-1-is-vulnerable-to-denial-of-service-via  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-30. Updated: 2026-10-30  
License: CC BY 4.0 with a link back

CVE-2026-117346 · Severity: info · Published 2026-10-30

Bitcoin Core is a cryptocurrency node software that maintains a complete record of all transactions. An attacker can craft malicious blockchain data that causes the software to create extremely large undo files without limits, exhausting disk space and forcing the node offline. This is a denial of service attack that prevents legitimate operation of Bitcoin network infrastructure.

Technologies: [Bitcoin Core](https://junglewise.ai/threats/technologies/bitcoin-core). Vendors: [Bitcoin](https://junglewise.ai/threats/vendors/bitcoin).

## Quick answers

**Is CVE-2026-117346 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-117346 being exploited in the wild.

**How severe is CVE-2026-117346?** Informational severity, published 30 October 2026.

**Which products and versions are affected?** Bitcoin Core through 31.1.

**Is there a fix for CVE-2026-117346?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-117346 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-117346?** Check whether you run Bitcoin Core at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

Bitcoin Core through version 31.1 fails to enforce size limits on undo files, which are used internally to reverse transaction state during blockchain reorganization. An attacker can exploit this by triggering conditions that cause undo files to grow without bound, consuming disk space until the node crashes or becomes unusable. This is a network-accessible denial of service requiring no authentication or user interaction.

## Affected products

- Bitcoin Bitcoin Core through 31.1

## Timeline

- 2026-10-30: disclosed

## References

- [http://bitcoin.com/](http://bitcoin.com/)
- [https://bitcoincore.org/en/2026/10/28/disclose-undo-overflow/](https://bitcoincore.org/en/2026/10/28/disclose-undo-overflow/)

## Related threats

- [Bitcoin Core unbounded memory growth on paused pre-BIP31 peers](https://junglewise.ai/threats/cve-2026-117349-bitcoin-core-prior-to-29-5-30-4-31-2-and-32-1-is-vulnerable-to)
- [Bitcoin Core remote crash in script interpreter](https://junglewise.ai/threats/cve-2024-52911-bitcoin-core-remote-crash-in-script-interpreter)