# 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.

- **Severity:** Medium 4.4 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:L/A:N`)
- **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 available:** No
- **Published:** 7 Feb 2023
- **Updated:** 10 Mar 2025
- **Also known as:** GHSA-wm83-3764-5wqh

## 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 (Interpretation Conflict)

## Which versions are affected by CVE-2023-22735?

It affects 1 product.


Products: 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.

## 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](https://insights.sbomify.com/CVE-2019-18933/): Information disclosure in n/a (critical 9.8)
- [CVE-2020-15070](https://insights.sbomify.com/CVE-2020-15070/): Code injection in n/a (high 8.8)
- [CVE-2017-0910](https://insights.sbomify.com/CVE-2017-0910/): Missing authorization in Zulip Server (high 8.8)
- [CVE-2025-31478](https://insights.sbomify.com/CVE-2025-31478/): Zulip Authentication Backend Configuration Bypass (high 8.2)
- [CVE-2023-33186](https://insights.sbomify.com/CVE-2023-33186/): Cross-site scripting vulnerability in Zulip Server development branch via topic tooltip (high 8.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-22735 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2023-22735 in the wild and no public exploit code.

Affected product: zulip. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2023-22735/ (Markdown: https://insights.sbomify.com/CVE-2023-22735/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-22735
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-22735
- OSV: https://osv.dev/vulnerability/CVE-2023-22735

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-22735/
Summaries are generated and may contain mistakes; the official description above is the record.