# CVE-2023-28833: Unrestricted filenames for logo or favicon as admin in the theming settings in nextcloud server

> Admins can overwrite files in the appdata directory via unrestricted filenames in logo or favicon uploads, potentially allowing malicious file replacement.

- **Severity:** Low 2.4 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 30 Mar 2023
- **Updated:** 11 Feb 2025
- **Also known as:** GHSA-ch7f-px7m-hg25

## What is CVE-2023-28833?

CVE-2023-28833 is a low-severity path traversal vulnerability in Nextcloud Nextcloud Server, published on 30 Mar 2023. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.

### Official description

Nextcloud server is an open source home cloud implementation. In affected versions admins of a server were able to upload a logo or a favicon and to provided a file name which was not restricted and could overwrite files in the appdata directory. Administrators may have access to overwrite these files by other means but this method could be exploited by tricking an admin into uploading a maliciously named file. It is recommended that the Nextcloud Server is upgraded to 24.0.10 or 25.0.4. Users unable to upgrade should avoid ingesting logo files from untrusted sources.

Weakness: CWE-434 (Unrestricted Upload of File with Dangerous Type), CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2023-28833?

It affects 1 product.


Products: Nextcloud Nextcloud Server.

## How do I fix CVE-2023-28833?

No fix has been published for CVE-2023-28833 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-28833 being exploited?

There is no known exploitation of CVE-2023-28833 in the wild and no public exploit code.

## Other vulnerabilities in Nextcloud Nextcloud Server

- [CVE-2021-32802](https://insights.sbomify.com/CVE-2021-32802/): Preview generation used third-party library not suited for user-generated content in Nextcloud server (critical 9.3)
- [CVE-2023-26482](https://insights.sbomify.com/CVE-2023-26482/): Scope of workflow operations is not validated in nextcloud server (critical 9.1)
- [CVE-2018-3775](https://insights.sbomify.com/CVE-2018-3775/): Auth bypass in Nextcloud Server (high 8.8)
- [CVE-2023-35172](https://insights.sbomify.com/CVE-2023-35172/): Nextcloud Server password reset endpoint is not brute force protected (high 8.7)
- [CVE-2023-32320](https://insights.sbomify.com/CVE-2023-32320/): Nextcloud Server's brute force protection allows someone to send more requests than intended (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-28833 and fix it if it is affected.

What it is: CVE-2023-28833 is a low-severity path traversal vulnerability in Nextcloud Nextcloud Server, published on 30 Mar 2023. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2023-28833 in the wild and no public exploit code.

Affected product: Nextcloud Nextcloud Server. 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-2023-28833/ (Markdown: https://insights.sbomify.com/CVE-2023-28833/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-28833
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-28833
- OSV: https://osv.dev/vulnerability/CVE-2023-28833

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-28833/
Summaries are generated and may contain mistakes; the official description above is the record.