# CVE-2018-8340: ADFS Security Feature Bypass Vulnerability

CVE-2018-8340 is fixed in 6 products on 1 platform, first by KB4343887, released August 14, 2018. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2018-8340
- Priority: Routine
- CVSS: 6.5 (Important)
- EPSS: 0.0789
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Vendor exploitability assessment: Exploitation Less Likely
- Published: Aug 14, 2018
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2018-8340

## Description

<p>A security feature bypass vulnerability exists when Active Directory Federation Services (ADFS) improperly handles multi-factor authentication requests.</p> <p>To exploit this vulnerability, an attacker could send a specially crafted authentication request. An attacker who successfully exploited this vulnerability could bypass some, but not all, of the authentication factors.</p> <p>This security update corrects how ADFS handles multi-factor authentication requests.</p>

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Microsoft | Windows Server 2012 R2 |  | [KB4343888](https://patchblox.com/security/data/fix/microsoft/kb4343888.md) | Aug 14, 2018 |
| Microsoft | Windows Server 2012 R2 |  | [KB4343898](https://patchblox.com/security/data/fix/microsoft/kb4343898.md) | Aug 14, 2018 |
| Microsoft | Windows Server 2012 R2 (Server Core installation) |  | [KB4343888](https://patchblox.com/security/data/fix/microsoft/kb4343888.md) | Aug 14, 2018 |
| Microsoft | Windows Server 2012 R2 (Server Core installation) |  | [KB4343898](https://patchblox.com/security/data/fix/microsoft/kb4343898.md) | Aug 14, 2018 |
| Microsoft | Windows Server 2016 | 14393.2430 | [KB4343887](https://patchblox.com/security/data/fix/microsoft/kb4343887.md) | Aug 14, 2018 |
| Microsoft | Windows Server 2016 (Server Core installation) | 14393.2430 | [KB4343887](https://patchblox.com/security/data/fix/microsoft/kb4343887.md) | Aug 14, 2018 |
| Microsoft | Windows Server, version 1709  (Server Core Installation) | 16299.611 | [KB4343897](https://patchblox.com/security/data/fix/microsoft/kb4343897.md) | Aug 14, 2018 |
| Microsoft | Windows Server, version 1803  (Server Core Installation) | 17134.228 | [KB4343909](https://patchblox.com/security/data/fix/microsoft/kb4343909.md) | Aug 14, 2018 |

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Data as of 2026-11-07T12:40:37Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo