CVE-2026-61628

nginx ignition is a user interface for the nginx web server. Prior to version 2.41.1, `POST /api/users/onboarding/finish` is registered as anonymous (unauthenticated) and creates a user with full ReadWrite admin permissions. Because the handler uses a check-then-act (TOCTOU) pattern between the "onboarding already completed?" check and the user-creation write, with no atomic guard, a remote unauthenticated attacker who can reach an instance in its pre-onboarding state can create an administrator account for themselves — and concurrent requests can create multiple admin accounts in a single race. Version 2.41.1 patches the issue.

• https://github.com/lucasdillmann/nginx-ignition/commit/0586b4e55ab780676d3553a2592979dfa2fb0183
• https://github.com/lucasdillmann/nginx-ignition/security/advisories/GHSA-pxcx-fv34-x9p5
• https://github.com/lucasdillmann/nginx-ignition/security/advisories/GHSA-pxcx-fv34-x9p5