What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 8.6 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 15.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2020-05-21 · updated 2026-08-19

Description

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. 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. The update addresses the vulnerability by changing the way TLS key exchange messages are validated.

Affected products

• Microsoft Windows 10 Version 1607: 1709, 1803, 1809, 1903, 1909
• Microsoft Windows Server 2019: 1903, 1909
• Microsoft Windows 10 1709: from 10.0.0 before publication — fixed in publication
• Microsoft Windows 10 Version 1709 for 32-bit Systems: from 10.0.0 before publication — fixed in publication
• Microsoft Windows 10 1803: from 10.0.0 before publication — fixed in publication
• Microsoft Windows 10: from 10.0.17763.0 before publication — fixed in publication
• Microsoft Windows 10 Version 1903 for 32-bit Systems: from 10.0.0 before publication — fixed in publication
• Microsoft Windows 10 Version 1903 for ARM64-based Systems: from 10.0.0 before publication — fixed in publication
• Microsoft Windows 10 Version 1903 for x64-based Systems: from 10.0.0 before publication — fixed in publication
• Microsoft Windows 10 1909: from 10.0.0 before publication — fixed in publication
• Microsoft Windows Server 2019: from 10.0.17763.0 before publication — fixed in publication
• Microsoft Windows Server, version 1803 (Server Core Installation): from 10.0.0 before publication — fixed in publication
• Microsoft Windows Server, version 1903 (Server Core installation): from 10.0.0 before publication — fixed in publication
• Microsoft Windows Server, version 1909 (Server Core installation): from 10.0.0 before publication — fixed in publication

How to fix

Upgrade to a fixed version: Microsoft Windows 10 1709 publication; Microsoft Windows 10 Version 1709 for 32-bit Systems publication; Microsoft Windows 10 1803 publication; Microsoft Windows 10 publication; Microsoft Windows 10 Version 1903 for 32-bit Systems publication; Microsoft Windows 10 Version 1903 for ARM64-based Systems publication; Microsoft Windows 10 Version 1903 for x64-based Systems publication; Microsoft Windows 10 1909 publication; Microsoft Windows Server 2019 publication; Microsoft Windows Server, version 1803 (Server Core Installation) publication; Microsoft Windows Server, version 1903 (Server Core installation) publication; Microsoft Windows Server, version 1909 (Server Core installation) publication. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2020-1118
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1118

Get alerted when CVE-2020-1118 or the next vulnerability affects your stack