Multiple vulnerabilities in Zulip Server

Published: 2023-05-20

Risk	Medium
Patch available	YES
Number of vulnerabilities	2
CVE-ID	CVE-2023-32677 CVE-2023-28623
CWE-ID	CWE-269 CWE-285
Exploitation vector	Network
Public exploit	N/A
Vulnerable software Subscribe	Zulip Server Web applications / Other software
Vendor	Zulip

Security Bulletin

This security bulletin contains information about 2 vulnerabilities.

1) Improper Privilege Management

EUVDB-ID: #VU76394

Risk: Low

CVSSv3.1: 3.8 [CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2023-32677

CWE-ID: CWE-269 - Improper Privilege Management

Exploit availability: No

Description

The vulnerability allows a remote user to bypass implemented security restrictions.

The vulnerability exists due to improper privilege management when sending invitations. A remote user can add other users to streams when they are not authorized to do so.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Zulip Server: 1.9.0 - 6.1

External links

http://github.com/zulip/zulip/commit/7c2693a2c64904d1d0af8503b57763943648cbe5
http://zulip.com/help/restrict-account-creation#change-who-can-send-invitations
http://github.com/zulip/zulip/security/advisories/GHSA-mrvp-96q6-jpvc
http://github.com/zulip/zulip/releases/tag/6.2

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.

2) Improper authorization

EUVDB-ID: #VU76393

Risk: Medium

CVSSv3.1: 5.7 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2023-28623

CWE-ID: CWE-285 - Improper Authorization

Exploit availability: No

Description

The vulnerability allows a remote attacker to bypass authorization checks.

The vulnerability exists due to an error in the registration process. A remote attacker can register a new account in the organization with an arbitrary email address in their control that's not in the organization's LDAP directory.

Successful exploitation of the vulnerability requires that 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 that the organization permissions don't require invitations to join.