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Vulnerability record · CVE-2023-28623 · published 19 May 2023

CVE-2023-28623: Zulip improper authorization vulnerability

Zulip · 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 `AUTHENTICATION_BACKENDS` 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.

3.7 CVSS 3.1 Low EPSS 0.53% · top 57.6% CWE-285 · Improper authorizationCWE-862 · Missing authorization
3.7CVSS 3.1 base score
0.53%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References
17 Jun 2026Last modified by NVD

Description

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 `AUTHENTICATION_BACKENDS` 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.

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/zulip/zulip/commit/3df1b4dd7c210c21deb6f829df19412b74573f8d PatchThird Party Advisory
https://github.com/zulip/zulip/security/advisories/GHSA-7p62-pjwg-56rv Third Party Advisory
https://github.com/zulip/zulip/commit/3df1b4dd7c210c21deb6f829df19412b74573f8d PatchThird Party Advisory
https://github.com/zulip/zulip/security/advisories/GHSA-7p62-pjwg-56rv Third Party Advisory

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2023-28623), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.