CVE-2026-85056: ZITADEL: MFA bypass via session reuse in Login V2
Summary
A vulnerability in ZITADEL’s Login V2 UI allowed a password-verified browser session to be reused for a new authentication request without re-checking a user’s enrolled second factor (TOTP, OTP, or U2F). An attacker who already knows valid credentials can fully authenticate to an application without completing MFA.
Impact
ZITADEL Login V2 issues a session as soon as the user’s password is verified, before the MFA challenge is completed. If the MFA step is abandoned (for example by navigating back) and login is started again, Login V2 may reuse that existing session instead of requiring the second factor.
Session validity checks only enforced MFA verification when the organization’s login policy had Force MFA (or Force MFA for local users only) enabled. They did not treat a voluntarily enrolled second factor as required. In the common case where MFA is available on the user but not organization-mandated, a password-only session was treated as fully authenticated and used to complete the OIDC or SAML callback, bypassing the user’s second factor.
Scope note: This issue affects customer applications that authenticate users through the hosted Login V2 UI (OIDC/SAML). It does not affect Login V1. It also does not affect authentication to ZITADEL itself — including the Console, the Management/Admin APIs, and user self-management — even when Login V2 is enabled.
Affected Versions
Systems running one of the following versions are affected:
4.x: 4.0.0 through 4.16.0 (including RC versions)
Patches
The vulnerability has been addressed in the latest releases. The patch ensures Login V2 validates that any second factor enrolled on the user has been verified before an existing session can be reused to complete authentication.
4.x: Upgrade to $\ge$ 4.16.1
Workarounds
If an immediate upgrade is not possible, enable Force MFA (or Force MFA for local users only, if you want to exempt IdP/federated logins) in the affected organization’s — or the instance default — login policy. This makes second-factor verification mandatory for password logins and closes this session-reuse bypass.
Note that this is a broader policy change (MFA becomes mandatory for the scoped local logins) rather than a narrow fix limited to users who already self-enrolled a second factor.
Questions
If you have any questions or comments about this advisory, please email us at security@zitadel.com
Credits
Thanks to Philippe Wechsler (@MadMonkey87) for finding and reporting the vulnerability.
Other sources
ZITADEL is an open source identity management platform. From 4.0.0 until 4.16.1, ZITADEL Login V2 creates a browser session after password verification and can reuse that session for a later authentication request without verifying a user's enrolled TOTP, OTP, or U2F second factor. When the MFA step is abandoned and login starts again, session-validity checks require MFA only when the organization enables Force MFA or Force MFA for local users only, so a voluntarily enrolled factor can be skipped while completing an OIDC or SAML callback for a customer application. Login V1, the ZITADEL Console, Management and Admin APIs, and user self-management are not affected. This issue is fixed in version 4.16.1.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
go/github.com/zitadel/zitadelto a version that resolves this vulnerability.Fixed in 1.80.0-v2.20.0.20260717062356-56f4798ed31f - Upgrade
Upgrade
ZITADEL Login V2to a version that resolves this vulnerability.Fixed in 4.16.1 - Configuration
Enable Force MFA in the affected organization's login policy or the instance default login policy. Alternatively, enable Force MFA for local users only to exempt IdP/federated logins.
ZITADEL Login V2 login policy Force MFA = enabled
Event History
Frequently Asked Questions
Which deployments are exposed to this issue?
Deployments using ZITADEL Login V2 from 4.0.0 through versions before 4.16.1 are affected. Login V1, the ZITADEL Console, Management and Admin APIs, and user self-management are not affected.
What does an attacker need to do to bypass MFA?
The attacker must be able to complete password verification, then abandon the MFA step and begin authentication again. The previously created browser session can then be reused to complete an OIDC or SAML callback without verifying an enrolled TOTP, OTP, or U2F factor.
Does enabling MFA prevent the bypass?
A voluntarily enrolled MFA factor can be skipped under the affected session-reuse flow. Session-validity checks require MFA when the organization enables Force MFA or Force MFA for local users only.
What is the remediation?
Upgrade ZITADEL Login V2 to version 4.16.1, which fixes the issue.