# CVE-2021-32726: Webauthn tokens not removed after user has been deleted

> Attackers can hijack accounts by reusing deleted usernames because WebAuthn tokens were not removed, allowing unauthorized access to Nextcloud servers.

- **Severity:** High 7.1 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/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:** Yes
- **Published:** 12 Jul 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-6qr9-c846-j8mg

## What is CVE-2021-32726?

CVE-2021-32726 is a high-severity authentication bypass vulnerability in Nextcloud Nextcloud Server, published on 12 Jul 2021. 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 Server is a Nextcloud package that handles data storage. In versions prior to 19.0.13, 20.011, and 21.0.3, webauthn tokens were not deleted after a user has been deleted. If a victim reused an earlier used username, the previous user could gain access to their account. The issue was fixed in versions 19.0.13, 20.0.11, and 21.0.3. There are no known workarounds.

Weakness: CWE-287 (Improper Authentication), CWE-708 (Incorrect Ownership Assignment)

## Which versions are affected by CVE-2021-32726?

It affects 1 product.


Products: Nextcloud Nextcloud Server.

## How do I fix CVE-2021-32726?

Upgrade to a fixed version.

## Is CVE-2021-32726 being exploited?

There is no known exploitation of CVE-2021-32726 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-2021-32726 and fix it if it is affected.

What it is: CVE-2021-32726 is a high-severity authentication bypass vulnerability in Nextcloud Nextcloud Server, published on 12 Jul 2021. 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-2021-32726 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-2021-32726/ (Markdown: https://insights.sbomify.com/CVE-2021-32726/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-32726
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-32726
- OSV: https://osv.dev/vulnerability/CVE-2021-32726

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-32726/
Summaries are generated and may contain mistakes; the official description above is the record.