# CVE-2023-28999: Nextcloud: Lack of authenticity of metadata keys allows a malicious server to gain access to E2EE folders

> A malicious server admin can bypass E2EE protections to decrypt, read, and modify files in encrypted folders via Nextcloud clients.

- **Severity:** Medium 6.9 (`CVSS:3.1/AV:P/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:L`)
- **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:** BIT-nextcloud-2023-28999, DEBIAN-CVE-2023-28999, GHSA-8875-wxww-3rr8, UBUNTU-CVE-2023-28999

## What is CVE-2023-28999?

CVE-2023-28999 is a medium-severity missing authorization 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

Nextcloud is an open-source productivity platform. In Nextcloud Desktop client 3.0.0 until 3.8.0, Nextcloud Android app 3.13.0 until 3.25.0, and Nextcloud iOS app 3.0.5 until 4.8.0, 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.​ This issue is fixed in Nextcloud Desktop 3.8.0, Nextcloud Android 3.25.0, and Nextcloud iOS 4.8.0. No known workarounds are available.

Weakness: CWE-311 (Missing Encryption of Sensitive Data), CWE-325 (Missing Cryptographic Step)

## Which versions are affected by CVE-2023-28999?

1 open source package ship an affected version, including nextcloud. It affects 2 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `nextcloud` | Bitnami | From 3.0.5 | 4.8.0 |

Products: Nextcloud Desktop, Nextcloud Nextcloud.

## How do I fix CVE-2023-28999?

Upgrade nextcloud to 4.8.0 or later.

## Is CVE-2023-28999 being exploited?

There is no known exploitation of CVE-2023-28999 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-2020-8227](https://insights.sbomify.com/CVE-2020-8227/): Path traversal in Desktop Client (medium 6.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-28999 and fix it if it is affected.

What it is: CVE-2023-28999 is a medium-severity missing authorization 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-2023-28999 in the wild and no public exploit code.

Affected packages and fixed versions:
- nextcloud (Bitnami): affected from 3.0.5; fixed in 4.8.0

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-2023-28999/ (Markdown: https://insights.sbomify.com/CVE-2023-28999/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-28999
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-28999
- OSV: https://osv.dev/vulnerability/CVE-2023-28999

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-28999/
Summaries are generated and may contain mistakes; the official description above is the record.