CVE-2023-28623: Unauthorized user can register an account in specific configurations in Zulip
Zulip is an open-source team collaboration tool with unique topic-based threading. In the event that 1: ZulipLDAPAuthBackend and an external authentication backend (any aside of ZulipLDAPAuthBackend and EmailAuthBackend) are the only ones enabled in AUTHENTICATIONBACKENDS in /etc/zulip/settings.py and 2: The organization permissions don't require invitations to join. An attacker can create a new account in the organization with an arbitrary email address in their control that's not in the organization's LDAP directory. The impact is limited to installations which have this specific combination of authentication backends as described above in addition to having Invitations are required for joining this organization organization permission disabled. This issue has been addressed in version 6.2. Users are advised to upgrade. Users unable to upgrade may enable the Invitations are required for joining this organization organization permission to prevent this issue.
Affected Software
Remediation
Event History
Frequently Asked Questions
What is CVE-2023-28623?
CVE-2023-28623 is a vulnerability in Zulip, an open-source team collaboration tool, which allows the circumvention of authentication through an external backend.
What is the severity of CVE-2023-28623?
The severity of CVE-2023-28623 is medium with a CVSS score of 3.7.
How does CVE-2023-28623 affect Zulip?
CVE-2023-28623 affects Zulip versions up to 6.2 and allows the circumvention of authentication when certain authentication backends are enabled.
How can I fix CVE-2023-28623?
To fix CVE-2023-28623, ensure that the only enabled authentication backends in Zulip's `AUTHENTICATION_BACKENDS` configuration are `ZulipLDAPAuthBackend` and `EmailAuthBackend`.
Are there any references for CVE-2023-28623?
Yes, you can find more information about CVE-2023-28623 in the following references: [GitHub Commit](https://github.com/zulip/zulip/commit/3df1b4dd7c210c21deb6f829df19412b74573f8d) and [GitHub Security Advisory](https://github.com/zulip/zulip/security/advisories/GHSA-7p62-pjwg-56rv).