# CVE-2020-1118: Microsoft Windows Transport Layer Security Denial of Service Vulnerability

CVE-2020-1118 is fixed in 20 products on 1 platform, first by KB4556812, released May 12, 2020. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2020-1118
- Priority: High
- CVSS: 8.6 (Important)
- EPSS: 0.1515
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Vendor exploitability assessment: Exploitation Less Likely
- Published: May 12, 2020
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2020-1118

## Description

<p>A denial of service vulnerability exists in the Windows implementation of Transport Layer Security (TLS) when it improperly handles certain key exchanges. An attacker who successfully exploited the vulnerability could cause a target system to stop responding.</p> <p>To exploit this vulnerability, a remote unauthenticated attacker could send a specially crafted request to a target system utilizing TLS 1.2 or lower, triggering the system to automatically reboot.</p> <p>The update addresses the vulnerability by changing the way TLS key exchange messages are validated.</p>

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Microsoft | Windows 10 Version 1709 for 32-bit Systems | 16299.1868 | [KB4556812](https://patchblox.com/security/data/fix/microsoft/kb4556812.md) | May 12, 2020 |
| Microsoft | Windows 10 Version 1709 for ARM64-based Systems | 16299.1868 | [KB4556812](https://patchblox.com/security/data/fix/microsoft/kb4556812.md) | May 12, 2020 |
| Microsoft | Windows 10 Version 1709 for x64-based Systems | 16299.1868 | [KB4556812](https://patchblox.com/security/data/fix/microsoft/kb4556812.md) | May 12, 2020 |
| Microsoft | Windows 10 Version 1803 for 32-bit Systems | 17134.1488 | [KB4556807](https://patchblox.com/security/data/fix/microsoft/kb4556807.md) | May 12, 2020 |
| Microsoft | Windows 10 Version 1803 for ARM64-based Systems | 17134.1488 | [KB4556807](https://patchblox.com/security/data/fix/microsoft/kb4556807.md) | May 12, 2020 |
| Microsoft | Windows 10 Version 1803 for x64-based Systems | 17134.1488 | [KB4556807](https://patchblox.com/security/data/fix/microsoft/kb4556807.md) | May 12, 2020 |
| Microsoft | Windows 10 Version 1809 for 32-bit Systems | 17763.1217 | [KB4551853](https://patchblox.com/security/data/fix/microsoft/kb4551853.md) | May 12, 2020 |
| Microsoft | Windows 10 Version 1809 for ARM64-based Systems | 17763.1217 | [KB4551853](https://patchblox.com/security/data/fix/microsoft/kb4551853.md) | May 12, 2020 |
| Microsoft | Windows 10 Version 1809 for x64-based Systems | 17763.1217 | [KB4551853](https://patchblox.com/security/data/fix/microsoft/kb4551853.md) | May 12, 2020 |
| Microsoft | Windows 10 Version 1903 for 32-bit Systems |  | [KB4556799](https://patchblox.com/security/data/fix/microsoft/kb4556799.md) | May 12, 2020 |
| Microsoft | Windows 10 Version 1903 for ARM64-based Systems |  | [KB4556799](https://patchblox.com/security/data/fix/microsoft/kb4556799.md) | May 12, 2020 |
| Microsoft | Windows 10 Version 1903 for x64-based Systems |  | [KB4556799](https://patchblox.com/security/data/fix/microsoft/kb4556799.md) | May 12, 2020 |
| Microsoft | Windows 10 Version 1909 for 32-bit Systems |  | [KB4556799](https://patchblox.com/security/data/fix/microsoft/kb4556799.md) | May 12, 2020 |
| Microsoft | Windows 10 Version 1909 for ARM64-based Systems |  | [KB4556799](https://patchblox.com/security/data/fix/microsoft/kb4556799.md) | May 12, 2020 |
| Microsoft | Windows 10 Version 1909 for x64-based Systems |  | [KB4556799](https://patchblox.com/security/data/fix/microsoft/kb4556799.md) | May 12, 2020 |
| Microsoft | Windows Server 2019 | 17763.1217 | [KB4551853](https://patchblox.com/security/data/fix/microsoft/kb4551853.md) | May 12, 2020 |
| Microsoft | Windows Server 2019 (Server Core installation) | 17763.1217 | [KB4551853](https://patchblox.com/security/data/fix/microsoft/kb4551853.md) | May 12, 2020 |
| Microsoft | Windows Server, version 1803  (Server Core Installation) | 17134.1488 | [KB4556807](https://patchblox.com/security/data/fix/microsoft/kb4556807.md) | May 12, 2020 |
| Microsoft | Windows Server, version 1903 (Server Core installation) |  | [KB4556799](https://patchblox.com/security/data/fix/microsoft/kb4556799.md) | May 12, 2020 |
| Microsoft | Windows Server, version 1909 (Server Core installation) |  | [KB4556799](https://patchblox.com/security/data/fix/microsoft/kb4556799.md) | May 12, 2020 |

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