---
id: CVE-2026-109371
title: >-
  ZITADEL 3.0.0 before 4.18.0 contains a missing authentication vulnerability in
  the hosted Login V1 UI, where the change-username handler acts on the account
  bound to a login flow before any factor is verified
summary: >-
  ZITADEL 3.0.0 before 4.18.0 contains a missing authentication vulnerability in
  the hosted Login V1 UI, where the change-username handler acts on the account
  bound to a login flow before any factor is verified. Unauthenticated attackers
  c…
severity: high
cvss: 8.2
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L'
cwe:
  - CWE-306
published: '2026-10-12'
updated: '2026-10-12'
sourceUpdated: '2026-10-12T17:17:34.700'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-109371'
references:
  - url: 'https://github.com/zitadel/zitadel/security/advisories/GHSA-4hgj-wm6c-q7p2'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/zitadel-3.0.0-before-4.18.0-unauthenticated-username-change-via-login-v1
    label: disclosure@vulncheck.com
tags:
  - nvd
ingestedAt: '2026-10-12T18:00:08.216Z'
---

## Overview

ZITADEL 3.0.0 before 4.18.0 contains a missing authentication vulnerability in the hosted Login V1 UI, where the change-username handler acts on the account bound to a login flow before any factor is verified. Unauthenticated attackers can submit a victim's login name and then post a new username to rename any active human user, including administrators, locking them out.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.