# CVE-2018-16465: Auth bypass in Nextcloud Server

> Attackers can bypass two-factor authentication if the second factor provider fails to load, allowing unauthorized access to Nextcloud accounts.

- **Severity:** Medium 5.3 (`CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/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:** 30 Oct 2018
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-v76x-gvw2-m5rp

## What is CVE-2018-16465?

CVE-2018-16465 is a medium-severity authentication bypass vulnerability in Nextcloud Nextcloud Server, published on 30 Oct 2018. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Missing state in Nextcloud Server prior to 14.0.0 would not enforce the use of a second factor at login if the the provider of the second factor failed to load.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2018-16465?

It affects 1 product.


Products: Nextcloud Nextcloud Server.

## How do I fix CVE-2018-16465?

No fix has been published for CVE-2018-16465 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-16465 being exploited?

There is no known exploitation of CVE-2018-16465 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-2018-16465 and fix it if it is affected.

What it is: CVE-2018-16465 is a medium-severity authentication bypass vulnerability in Nextcloud Nextcloud Server, published on 30 Oct 2018. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2018-16465 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-2018-16465/ (Markdown: https://insights.sbomify.com/CVE-2018-16465/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-16465
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-16465
- OSV: https://osv.dev/vulnerability/CVE-2018-16465

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-16465/
Summaries are generated and may contain mistakes; the official description above is the record.