Zulip up to 12.1 OpenID Connect Backend GenericOpenIdConnectBackend email_verified improper authentication

Summaryinfo

A vulnerability has been found in Zulip up to 12.1 and classified as critical. This affects the function GenericOpenIdConnectBackend of the component OpenID Connect Backend. The manipulation of the argument email_verified leads to improper authentication. This vulnerability is traded as CVE-2026-102893. It is possible to initiate the attack remotely. There is no exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Zulip up to 12.1. This issue affects the function GenericOpenIdConnectBackend of the component OpenID Connect Backend. The manipulation of the argument email_verified with an unknown input leads to a improper authentication vulnerability. Using CWE to declare the problem leads to CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

Zulip is an open-source team collaboration tool. In Zulip Server versions through 12.1, GenericOpenIdConnectBackend matches the identity provider email claim to an active account's delivery_email without rejecting an explicitly false email_verified claim. If a configured identity provider returns an email address that the authenticating user does not control together with email_verified=false, Zulip can log the user into the existing account for that address. Exploitation requires a misconfigured trusted identity provider, and deployments whose authoritative identity provider only emits email addresses controlled by the authenticating user are not affected. This issue is fixed in version 12.2.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-102893 since 09/29/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 12.2 eliminates this vulnerability.

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Productinfo

Name

• Zulip

Version

• 12.0
• 12.1

Website

• Product: https://github.com/zulip/zulip/

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