What is CVE-2026-109371?

CVE-2026-109371 is a high-severity vulnerability in Zitadel, classified under Missing Authentication for Critical Function. CVSS score: 8.2/10. Published 2026-10-12.

How severe is CVE-2026-109371?

High severity. CVSS v3 base score is 8.2 out of 10.

Auth bypass in Zitadel

CVE-2026-109371

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.

Vulnerability class: Broken Authentication

Published 2026-10-12 · last modified 2026-10-12.

CVSS v3 metric

CVSS v3 base score 8.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Zitadel

Weakness classification (CWE)

CWE-306 — Missing Authentication for Critical Function

References

github.com/zitadel/zitadel/security/advisories/GHSA-4hgj-wm6c-q7p2 (vendor-advisory)
www.vulncheck.com/advisories/zitadel-3.0.0-before-4.18.0-unauthenticated-userna… (third-party-advisory)

Frequently asked questions

What is CVE-2026-109371?: CVE-2026-109371 is a high-severity vulnerability in Zitadel, classified under Missing Authentication for Critical Function. CVSS score: 8.2/10. Published 2026-10-12.
How severe is CVE-2026-109371?: High severity. CVSS v3 base score is 8.2 out of 10.