CVE-2025-54605 - Disk filling from invalid blocks

Disclosure of the details of a log-filling bug which allowed an attacker to cause a victim node tofill up its disk space by repeatedly sending invalid blocks. Exploitability of this bug is limited,as it would take a long time before it would cause the victim to run out of disk space. A fix wasreleased on October 10th 2025 in Bitcoin Core v30.0. This issue is considered Low severity. Details A node would unconditionally log when receiving a block that fails basic sanity checks, or whenreceiving a block that branches off prior to the last checkpoint. By repeatedly sending such aninvalid block to a victim node, an attacker could cause the victim to run out of disk space. This issue was fixed by implementing log rate-limiting across the board, also preventing futureissues of the same type from happening. Attribution Niklas Goegge discovered this bug and disclosed it responsibly. Eugene Siegel independentlyre-discovered this bug and disclosed it responsibly. Eugene Siegel and Niklas Goegge worked on a fix mitigating all types of log-filling attacks. Credits also to contributor “practicalswift” who previously raised concernsabout disk-filling vectors in Bitcoin Core and worked to address them. Timeline 2022-05-16 - Niklas Goegge reports this issue to the Bitcoin Core security mailing list 2025-03-13 - Eugene Siegel reports this issue to the Bitcoin Core security mailing list 2025-04-24 - Eugene Siegel reports to the security mailing list about his research on the worstcase disk filling rate. 2025-05-23 - Eugene Siegel opens PR #32604 tointroduce log rate-limiting, based on earlier work from Niklas Goegge 2025-07-09 - PR #32604 is merged into master 2025-09-04 - Version 29.1 is released with the fix 2025-10-10 - Version 30.0 is released with the fix 2025-10-24 - Public Disclosure