CVE-2026-109371

HIGH 8.2

ZITADEL 3.0.0 before 4.18.0 Unauthenticated Username Change via Login V1

CVSS Score

8.2

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-306
Vendor	zitadel
Product	zitadel
Published	Oct 12, 2026

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CVSS v3 Breakdown

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

High

Availability

Low

Affected Versions

zitadel / zitadel

3.0.0 < 4.18.0

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/zitadel/zitadel/security/advisories/GHSA-4hgj-wm6c-q7p2 vulncheck.com: https://www.vulncheck.com/advisories/zitadel-3.0.0-before-4.18.0-unauthenticated-username-change-via-login-v1

Credits

muhlemmer grvijayan IAM-marco 🔍 AdamKorcz