CVE-2026-109371

High

Description

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.

SeverityHigh

CVSS8.2

Exploit probability—

ProductZitadel

PublishedOct 12, 2026

First seenOct 12, 2026

Weakness typeCWE-306Missing authentication for critical function

How to fix

Update

zitadel zitadel4.18.0 or later

Vendor advisories

github.com/zitadel/zitadel/security/advisories/GHSA-4hgj-wm6c-q7p2

Affected products

Product	Affected versions	Fixed in
zitadel zitadel	3.0.0 ≤ v < 4.18.0	4.18.0

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