CVE-2026-102893: Auth Bypass

Description

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.

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Weakness Type (CWE)

CWE-287 Improper Authentication

References

Other References

https://github.com/zulip/zulip/commit/68d2d9defa39f8af96a50fc7430efc34dee120b5 https://github.com/zulip/zulip/commit/b40f191a8c71e74fcb471f71de6a1233de157102 https://github.com/zulip/zulip/pull/39913 https://github.com/zulip/zulip/releases/tag/12.2 https://github.com/zulip/zulip/security/advisories/GHSA-xw9h-9rcm-hx4m

Frequently Asked Questions

What is CVE-2026-102893? +

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.

How do I check if I'm vulnerable to CVE-2026-102893? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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