# CVE-2023-35173: End-to-End encrypted file-drops can be made inaccessible

> An attacker can render previously dropped files inaccessible by providing invalid metadata, causing a denial of service for Nextcloud users.

- **Severity:** Medium 5.7 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H`)
- **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:** 23 Jun 2023
- **Updated:** 2 Aug 2024
- **Also known as:** GHSA-x7c7-v5r3-mg37

## What is CVE-2023-35173?

CVE-2023-35173 is a medium-severity denial of service vulnerability in nextcloud security-advisories, published on 23 Jun 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

Nextcloud End-to-end encryption app provides all the necessary APIs to implement End-to-End encryption on the client side. By providing an invalid meta data file, an attacker can make previously dropped files inaccessible. It is recommended that the Nextcloud End-to-end encryption app is upgraded to version 1.12.4 that contains the fix.

Weakness: CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2023-35173?

It affects 1 product.


Products: Nextcloud End-to-End Encryption.

## How do I fix CVE-2023-35173?

No fix has been published for CVE-2023-35173 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-35173 being exploited?

There is no known exploitation of CVE-2023-35173 in the wild and no public exploit code.

## Other vulnerabilities in nextcloud security-advisories

- [CVE-2021-22906](https://insights.sbomify.com/CVE-2021-22906/): Missing authorization in Nextcloud End-to-End Encryption (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-35173 and fix it if it is affected.

What it is: CVE-2023-35173 is a medium-severity denial of service vulnerability in nextcloud security-advisories, published on 23 Jun 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-2023-35173 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-2023-35173/ (Markdown: https://insights.sbomify.com/CVE-2023-35173/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-35173
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-35173
- OSV: https://osv.dev/vulnerability/CVE-2023-35173

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-35173/
Summaries are generated and may contain mistakes; the official description above is the record.