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TI-2023-13143 Aliases CVE-2023-28623

Unauthorized user can register an account in specific configurations in Zulip

Priority LOW 29CWE-285Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
Security bypass
Confidentiality · integrity · availability
High · Low · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-285.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00527 44th percentileScored 2026-11-07
Fix Fixed zulip (zulip): 6.2

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
zulipzulip2.1.0 to before 6.26.2Patch availableCNA
  • zulip Vendorzulip Affected 2.1.0 to before 6.2 Fixed in 6.2 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:zulip:zulip:*:*:*:*:*:*:*:*before 6.2Vulnerablezulip
  • cpe:2.3:a:zulip:zulip:*:*:*:*:*:*:*:* Versions before 6.2 Vulnerable ·zulip

Remediation

  • Fix · CNA zulip (zulip) Fixed in 6.2

Timeline

  1. 2026-10-02 Threatist record created from CVE-2023-28623

References

Patch 1

Advisory 1

  • TI-2026-20810 Zulip: Anonymous File Access After Disabling Spectator Access CVSS 3.1MEDIUM 5.3
  • TI-2026-21062 Zulip: Path Traversal in Import CVSS 3.1MEDIUM 6.1
  • TI-2021-19605 RabbitMQ exposes ports with weak default secrets in Zulip Server CVSS 3.1CRITICAL 9.8
  • TI-2023-15953 Users who can send invitations can erroneously add users to streams during invitation in Zulip CVSS 3.1LOW 3.1
  • TI-2022-13210 Zulip Server insufficient authorization for changing bot roles CVSS 3.1HIGH 8.8
  • TI-2021-02864 Improper Access Control in zulip/zulip CVSS 3.1HIGH 8.8
See all 19 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences