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CVE-2023-21819: Windows Secure Channel Denial of Service Vulnerability

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 30.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2023-02-14 · updated 2026-08-19
• Weakness: CWE-125

Description

Windows Secure Channel Denial of Service Vulnerability

Affected products

• Microsoft Windows 10: before 10.0.17763.4010 — fixed in 10.0.17763.4010
• Microsoft Windows 10 20H2: before 10.0.19042.2604 — fixed in 10.0.19042.2604
• Microsoft Windows 10: before 10.0.19044.2604 — fixed in 10.0.19044.2604
• Microsoft Windows 10: before 10.0.19045.2604 — fixed in 10.0.19045.2604
• Microsoft Windows 11 21H2: before 10.0.22000.1574 — fixed in 10.0.22000.1574
• Microsoft Windows Server 2019: all versions
• Microsoft Windows Server 2022: all versions
• Microsoft Windows 10: from 10.0.17763.0 before 10.0.17763.4010 — fixed in 10.0.17763.4010
• Microsoft Windows 10 20H2: from 10.0.0 before 10.0.19042.2604 — fixed in 10.0.19042.2604
• Microsoft Windows 10: from 10.0.19043.0 before 10.0.19044.2604 — fixed in 10.0.19044.2604
• Microsoft Windows 10: from 10.0.19045.0 before 10.0.19045.2604 — fixed in 10.0.19045.2604
• Microsoft Windows 11 21H2: from 10.0.0 before 10.0.22621.1574 — fixed in 10.0.22621.1574
• Microsoft Windows Server 2019: from 10.0.17763.0 before 10.0.17763.4010 — fixed in 10.0.17763.4010
• Microsoft Windows Server 2022: from 10.0.20348.0 before 10.0.20348.1547 — fixed in 10.0.20348.1547

How to fix

Upgrade to a fixed version: Microsoft Windows 10 10.0.17763.4010; Microsoft Windows 10 20H2 10.0.19042.2604; Microsoft Windows 10 10.0.19044.2604; Microsoft Windows 10 10.0.19045.2604; Microsoft Windows 11 21H2 10.0.22000.1574; Microsoft Windows 10 10.0.17763.4010; Microsoft Windows 10 20H2 10.0.19042.2604; Microsoft Windows 10 10.0.19044.2604; Microsoft Windows 10 10.0.19045.2604; Microsoft Windows 11 21H2 10.0.22621.1574; Microsoft Windows Server 2019 10.0.17763.4010; Microsoft Windows Server 2022 10.0.20348.1547. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21819
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21819

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