#VU52317 Improper access control in Zulip Server - CVE-2021-30478

Vulnerability identifier: #VU52317

Vulnerability risk: Low

CVSSv4.0: 1.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2021-30478

CWE-ID: CWE-284

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Zulip Server
Web applications / Other software

Vendor: Zulip

Description

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

The vulnerability exists due to improper access restrictions in the implementation of the "can_forge_sender" permission. A remote authenticated attacker can send messages appearing as if sent by a system bot, including to other organizations hosted by the same Zulip installation.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Zulip Server: 3.0 - 3.3

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External links
https://blog.zulip.com/2021/04/14/zulip-server-3-4/

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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.