Improper access control in Zulip Server

1) Improper access control

EUVDB-ID: #VU83257

Risk: Low

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

CVE-ID: CVE-2023-47642

CWE-ID: CWE-284 - Improper Access Control

Exploit availability: No

Description

The vulnerability allows a remote user to gain unauthorized access to otherwise restricted functionality.

The vulnerability exists due to improper access restrictions. Active users who had previously been subscribed to a stream incorrectly continued being able to use the Zulip API to access metadata for that stream after they were removed from the stream.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Zulip Server: 1.3.0 - 7.4

External links

http://github.com/zulip/zulip/security/advisories/GHSA-c9wc-65fh-9x8p
http://github.com/zulip/zulip/commit/6336322d2f9bbccaacfc80cba83a3c62eefd5737

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.