High severity · published Oct 12, 2026
CVE-2026-109371
ZITADEL 3.0.0 before 4.18.0 Unauthenticated Username Change via Login V1
8.2
CVSS
0.4%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
High
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 30% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
ZI
zitadel · zitadel
3.0.0 before 4.18.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-109371
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-109371
vendor-advisory
https://github.com/zitadel/zitadel/security/advisories/GHSA-4hgj-wm6c-q7p2
third-party-advisory
https://www.vulncheck.com/advisories/zitadel-3.0.0-before-4.18.0-unauthenticated-username-change-via-login-v1
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