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High8.6Microsoft Server

High [CVE-2020-1118] Microsoft Windows Transport Layer Security Denial of Service Vulnerability

This high-severity Microsoft Server advisory covers CVE-2020-1118 affecting Windows Server 2019 (Server Core installation), Windows Server, version 1803 (Server Core Installation), Windows Server, version 1903 (Server Core installation).

CVE-2020-1118 Published May 21, 2020Updated by vendor Aug 19, 2026
Affected products & platforms
Microsoft ServerWindows Server
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Summary

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 named by the advisory: Windows Server 2019; Windows Server 2019 (Server Core installation); Windows Server, version 1803 (Server Core Installation); Windows Server, version 1903 (Server Core installation); and 1 more.

Affected products named by the advisory: Windows Server, version 1909 (Server Core installation).

Affected versions
  • Windows 10 Version 1709 10.0.0 before publication
  • Windows 10 Version 1709 for 32-bit Systems 10.0.0 before publication
  • Windows 10 Version 1803 10.0.0 before publication
  • Windows 10 Version 1809 10.0.17763.0 before publication
  • Windows 10 Version 1809 10.0.0 before publication
  • Windows 10 Version 1903 for 32-bit Systems 10.0.0 before publication
  • Windows 10 Version 1903 for ARM64-based Systems 10.0.0 before publication
  • Windows 10 Version 1903 for x64-based Systems 10.0.0 before publication
  • Windows 10 Version 1909 10.0.0 before publication
  • Windows Server 2019 10.0.17763.0 before publication
  • Windows Server 2019 (Server Core installation) 10.0.17763.0 before publication
  • Windows Server, version 1803 (Server Core Installation) 10.0.0 before publication

Official advisory · high-confidence parse· fetched 1 hour ago·verify at source

Fixed versions
  • publication

Official advisory · high-confidence parse· fetched 1 hour ago·verify at source

Mitigation checklist

Recommended fix / mitigation
  • The update addresses the vulnerability by changing the way TLS key exchange messages are validated.

Official advisory · high-confidence parse· fetched 1 hour ago·verify at source

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