Dangerous file upload in Zulip Server

1) Arbitrary file upload

EUVDB-ID: #VU72011

Risk: Medium

CVSSv3.1: 4.7 [CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2023-22735

CWE-ID: CWE-434 - Unrestricted Upload of File with Dangerous Type

Exploit availability: No

Description

The vulnerability allows a remote user to perform XSS attacks.

The vulnerability exists due to application allows to upload files with arbitrary Content-Type. Such file will be served from the Zulip hostname with Content-Disposition: inline and no Content-Security-Policy header. A remote user can upload a malicious file and execute arbitrary Javascript in the victim's browser in security context of the website.

Mitigation

Install updates from vendor's website.

The vulnerability affects the main branch between 2023-01-09 and 2023-02-07.

Vulnerable software versions

Zulip Server: 6.1

External links

http://github.com/zulip/zulip/security/advisories/GHSA-wm83-3764-5wqh

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.