# CVE-2018-8340: Security feature bypass in Windows 10 Servers

> Attackers can bypass multi-factor authentication in AD FS due to improper request handling, affecting Windows Server environments.

- **Severity:** Medium 6.5 (`CVSS:3.0/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:** 15 Aug 2018
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-4rgc-rj2m-g9gr

## What is CVE-2018-8340?

CVE-2018-8340 is a medium-severity vulnerability in Microsoft Windows Server 2012, published on 15 Aug 2018. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A security feature bypass vulnerability exists when Active Directory Federation Services (AD FS) improperly handles multi-factor authentication requests, aka "AD FS Security Feature Bypass Vulnerability." This affects Windows Server 2016, Windows Server 2012 R2, Windows 10 Servers.

## Which versions are affected by CVE-2018-8340?

It affects 2 products.


Products: Microsoft Windows Server 2012, Microsoft Windows Server 2016.

## How do I fix CVE-2018-8340?

No fix has been published for CVE-2018-8340 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-8340 being exploited?

There is no known exploitation of CVE-2018-8340 in the wild and no public exploit code.

## Other vulnerabilities in Microsoft Windows Server 2012

- [CVE-2025-59287](https://insights.sbomify.com/CVE-2025-59287/): Microsoft Windows Server Update Service (WSUS) Deserialization of Untrusted Data (critical 9.8, exploited in the wild)
- [CVE-2026-69595](https://insights.sbomify.com/CVE-2026-69595/): Windows Services for NFS ONCRPC XDR Driver Remote Code Execution Vulnerability (critical 9.8)
- [CVE-2026-78445](https://insights.sbomify.com/CVE-2026-78445/): Windows Services for NFS ONCRPC XDR Driver Remote Code Execution Vulnerability (critical 9.8)
- [CVE-2026-41089](https://insights.sbomify.com/CVE-2026-41089/): Windows Netlogon Remote Code Execution Vulnerability (critical 9.8)
- [CVE-2024-43639](https://insights.sbomify.com/CVE-2024-43639/): Windows KDC Proxy Remote Code Execution Vulnerability (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-8340 and fix it if it is affected.

What it is: CVE-2018-8340 is a medium-severity vulnerability in Microsoft Windows Server 2012, published on 15 Aug 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-2018-8340 in the wild and no public exploit code.

Affected product: Microsoft Windows Server 2012. 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-2018-8340/ (Markdown: https://insights.sbomify.com/CVE-2018-8340/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-8340
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-8340
- OSV: https://osv.dev/vulnerability/CVE-2018-8340

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-8340/
Summaries are generated and may contain mistakes; the official description above is the record.