Advanced IP Blocker <= 8.13.13 - Unauthenticated Authentication Bypass via Missing Step-1 Binding to 2FA Login Handler

The Advanced IP Blocker plugin for WordPress is vulnerable to Authentication Bypass in all versions up to, and including, 8.13.13 The vulnerability exists because `handle_login_action()` performs no server-side check — via transient, session marker, or equivalent — that a requester completed step-1 password authentication before processing a step-2 TOTP submission for the POSTed `user_id`; compounding this, an error branch in the function unconditionally mints a fresh `advaipbl-2fa-interim-{user_id}` nonce and delivers it in a `Location` header to any unauthenticated caller, after which `display_2fa_login_form_step_2()` renders a valid `advaipbl-2fa-verify-{user_id}` nonce in HTML — both nonces computed against a fixed `uid=0` empty-session context and therefore fully reusable by the attacker across subsequent requests. This makes it possible for unauthenticated attackers to bypass authentication entirely for any 2FA-enabled account, including administrators, by brute-forcing an unthrottled 6-digit TOTP code (no attempt counter, no account lockout, and no `wp_login_failed` firing) and receiving a fully authenticated session cookie via `wp_set_auth_cookie` without ever supplying the account password, resulting in complete site takeover. Exploitation requires only a known `user_id` for an account that has the plugin's 2FA feature enabled.

Source published

10 Oct 2026 03:26:45 UTC

Source modified

11 Oct 2026 16:55:20 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H