# CVE-2021-41239: User enumeration setting not respected in Nextcloud server

> Attackers can enumerate users on Nextcloud instances even when user listings are disabled, exposing user data.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 Mar 2022
- **Updated:** 23 Apr 2025
- **Also known as:** GHSA-g722-cm3h-8wrx

## What is CVE-2021-41239?

CVE-2021-41239 is a medium-severity vulnerability in Nextcloud Nextcloud Server, published on 8 Mar 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Nextcloud server is a self hosted system designed to provide cloud style services. In affected versions the User Status API did not consider the user enumeration settings by the administrator. This allowed a user to enumerate other users on the instance, even when user listings where disabled. It is recommended that the Nextcloud Server is upgraded to 20.0.14, 21.0.6 or 22.2.1. There are no known workarounds.

Weakness: CWE-862 (Missing Authorization), CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)

## Which versions are affected by CVE-2021-41239?

It affects 1 product.


Products: Nextcloud Nextcloud Server.

## How do I fix CVE-2021-41239?

Upgrade to a fixed version.

## Is CVE-2021-41239 being exploited?

There is no known exploitation of CVE-2021-41239 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-2021-41239 and fix it if it is affected.

What it is: CVE-2021-41239 is a medium-severity vulnerability in Nextcloud Nextcloud Server, published on 8 Mar 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-41239 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-2021-41239/ (Markdown: https://insights.sbomify.com/CVE-2021-41239/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-41239
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-41239
- OSV: https://osv.dev/vulnerability/CVE-2021-41239

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-41239/
Summaries are generated and may contain mistakes; the official description above is the record.