# CVE-2023-28998: Nextcloud Desktop client misbehaves with E2EE when the server returns empty list of metadata keys

> A malicious server administrator can bypass end-to-end encryption to decrypt, read, and modify files in synchronized folders.

- **Severity:** Medium 6.7 (`CVSS:3.1/AV:P/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 4 Apr 2023
- **Updated:** 11 Feb 2025
- **Also known as:** DEBIAN-CVE-2023-28998, GHSA-jh3g-wpwv-cqgr, UBUNTU-CVE-2023-28998

## What is CVE-2023-28998?

CVE-2023-28998 is a medium-severity vulnerability in nextcloud security-advisories, published on 4 Apr 2023. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

The Nextcloud Desktop Client is a tool to synchronize files from Nextcloud Server. Starting with version 3.0.0 and prior to version 3.6.5, a malicious server administrator can gain full access to an end-to-end encrypted folder. They can decrypt files, recover the folder structure, and add new files.​ Users should upgrade the Nextcloud Desktop client to 3.6.5 to receive a patch. No known workarounds are available.

Weakness: CWE-325 (Missing Cryptographic Step)

## Which versions are affected by CVE-2023-28998?

It affects 1 product.


Products: Nextcloud Desktop.

## How do I fix CVE-2023-28998?

Upgrade to a fixed version.

## Is CVE-2023-28998 being exploited?

There is no known exploitation of CVE-2023-28998 in the wild and no public exploit code.

## Other vulnerabilities in nextcloud security-advisories

- [CVE-2024-46958](https://insights.sbomify.com/CVE-2024-46958/): Misconfiguration in n/a (critical 9.1)
- [CVE-2020-8224](https://insights.sbomify.com/CVE-2020-8224/): Code injection in Desktop Client (high 7.8)
- [CVE-2020-8225](https://insights.sbomify.com/CVE-2020-8225/): Information disclosure in Desktop Client (high 7.5)
- [CVE-2021-37617](https://insights.sbomify.com/CVE-2021-37617/): Untrusted Search Path in Nextcloud Desktop Client (high 7.3)
- [CVE-2023-28999](https://insights.sbomify.com/CVE-2023-28999/): Nextcloud: Lack of authenticity of metadata keys allows a malicious server to gain access to E2EE folders (medium 6.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-28998 and fix it if it is affected.

What it is: CVE-2023-28998 is a medium-severity vulnerability in nextcloud security-advisories, published on 4 Apr 2023. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2023-28998 in the wild and no public exploit code.

Affected product: nextcloud security-advisories. 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-2023-28998/ (Markdown: https://insights.sbomify.com/CVE-2023-28998/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-28998
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-28998
- OSV: https://osv.dev/vulnerability/CVE-2023-28998

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-28998/
Summaries are generated and may contain mistakes; the official description above is the record.