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 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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
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 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.
- Record
CVE-2023-28623- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N - Weakness
- CWE-285, CWE-862
- Updated
- 2026-11-02
EUVDEUVD-2023-32291
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.
- Record
EUVD-2023-32291- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N - Updated
- 2026-11-03
NVD
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.
- Record
CVE-2023-28623- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N - CVSS 3.1
- 3.7 Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N - Weakness
- CWE-285, CWE-862
- Updated
- 2026-11-02
OSV
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 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.
- Record
CVE-2023-28623- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N - Weakness
- CWE-285, CWE-862
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases, published | EUVD | |
| first indexed | CVE List, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2023-28623 is a medium vulnerability (CVSS 6.5) in Zulip, published May 19, 2023. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.53%, the 44th percentile. No source names a fixed version.