Postmortem for Kernel Soundness Bug #14576 | Hacker News

Lean kernel soundness bug #14576 allowed an invalid Collatz-related proof claim to collapse into a proof of `False`.

The root cause was traced to nested inductive types, and the issue was reduced to a small reproducible proof of `False`.

The bug was fixed during the week of July 27.

The postmortem underscores that proof assistants still depend on a highly trusted kernel, so soundness bugs must be audited and patched quickly.