Auth bypass in Zitadel
CVE-2026-56666
ZITADEL is an open source identity management platform. Prior to 4.15.3, ZITADEL's external identity provider handler checks that the local user's email is verified but does not verify that the external IdP confirmed ownership of the same email before auto-linking by email, allowing a permissive provider account with a victim email address to be linked to the victim's local account. This issue is fixed in version 4.15.3.
Vulnerability class: Broken Authentication
EPSS: 0.003 (20.5th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 4.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N.
Affected products
- Zitadel — versions < 4.15.3
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
Frequently asked questions
- What is CVE-2026-56666?
- CVE-2026-56666 is a medium-severity vulnerability in Zitadel, classified under Improper Authentication. CVSS score: 4.8/10. Published 2026-07-10.
- How severe is CVE-2026-56666?
- Medium severity. CVSS v3 base score is 4.8 out of 10.