# CVE-2021-37630: Secret Circle can be joined without approval in Nextcloud Circles

> Attackers can join secret circles without approval, leaking private information in Nextcloud Circles applications.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 7 Sep 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-56j9-3rj4-wvgm

## What is CVE-2021-37630?

CVE-2021-37630 is a medium-severity missing authorization vulnerability in nextcloud security-advisories, published on 7 Sep 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Nextcloud Circles is an open source social network built for the nextcloud ecosystem. In affected versions the Nextcloud Circles application allowed any user to join any "Secret Circle" without approval by the Circle owner leaking private information. It is recommended that Nextcloud Circles is upgraded to 0.19.15, 0.20.11 or 0.21.4. There are no workarounds for this issue.

Weakness: CWE-639 (Authorization Bypass Through User-Controlled Key)

## Which versions are affected by CVE-2021-37630?

It affects 1 product.


Products: Nextcloud Circles.

## How do I fix CVE-2021-37630?

No fix has been published for CVE-2021-37630 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-37630 being exploited?

There is no known exploitation of CVE-2021-37630 in the wild and no public exploit code.

## Other vulnerabilities in nextcloud security-advisories

- [CVE-2021-32782](https://insights.sbomify.com/CVE-2021-32782/): Cross-Site Scripting in Nextcloud Circles (medium 5.8)
- [CVE-2019-15610](https://insights.sbomify.com/CVE-2019-15610/): Missing authorization in Nextcloud Circles (medium 4.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-37630 and fix it if it is affected.

What it is: CVE-2021-37630 is a medium-severity missing authorization vulnerability in nextcloud security-advisories, published on 7 Sep 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-37630 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-2021-37630/ (Markdown: https://insights.sbomify.com/CVE-2021-37630/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-37630
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-37630
- OSV: https://osv.dev/vulnerability/CVE-2021-37630

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-37630/
Summaries are generated and may contain mistakes; the official description above is the record.