What’s Vulnerable › Vulnerabilities

CVE-2026-109371: ZITADEL 3.0.0 before 4.18.0 Unauthenticated Username Change via Login V1

• Severity: high (CVSS 8.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-12 · updated 2026-10-15
• Weakness: CWE-306

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.

Affected products

• zitadel: from 3.0.0 before 4.18.0 — fixed in 4.18.0

How to fix

Upgrade to a fixed version: zitadel 4.18.0. Check the vendor advisory for mitigations.

References

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

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