CVE-2023-22735 Cross-site scripting in zulip
Attackers can execute arbitrary JavaScript in the context of Zulip by uploading files with malicious content types, enabling session theft.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2023-22735?
CVE-2023-22735 is a medium-severity cross-site scripting vulnerability in zulip, published on 7 Feb 2023. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
Zulip is an open-source team collaboration tool. In versions of zulip prior to commit `2f6c5a8` but after commit `04cf68b` users could upload files with arbitrary `Content-Type` which would be served from the Zulip hostname with `Content-Disposition: inline` and no `Content-Security-Policy` header, allowing them to trick other users into executing arbitrary Javascript in the context of the Zulip application. Among other things, this enables session theft. Only deployments which use the S3 storage (not the local-disk storage) are affected, and only deployments which deployed commit 04cf68b45ebb5c03247a0d6453e35ffc175d55da, which has only been in `main`, not any numbered release. Users affected should upgrade from main again to deploy this fix. Switching from S3 storage to the local-disk storage would nominally mitigate this, but is likely more involved than upgrading to the latest `main` which addresses the issue.
Weakness: CWE-436
Which versions are affected by CVE-2023-22735?
It affects 1 product.
Products include Zulip Zulip Server.
How do I fix CVE-2023-22735?
No fix has been published for CVE-2023-22735 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2023-22735 being exploited?
There is no known exploitation of CVE-2023-22735 in the wild and no public exploit code.
Other vulnerabilities in zulip
- CVE-2019-18933 Information disclosure in n/a
- CVE-2020-15070 Code injection in n/a
- CVE-2017-0910 Missing authorization in Zulip Server
- CVE-2025-31478 Zulip Authentication Backend Configuration Bypass
- CVE-2023-33186 Cross-site scripting vulnerability in Zulip Server development branch via topic tooltip
Sources
Also known as GHSA-wm83-3764-5wqh.