Microsoft Windows DNS
CVE-2020-0993 — Windows DNS Denial of Service Vulnerability
Executive Summary
A denial of service vulnerability exists in Windows DNS when it fails to properly handle queries. An attacker who successfully exploited this vulnerability could cause the DNS service to become nonresponsive. To exploit the vulnerability, an authenticated attacker could send malicious DNS queries to a target, resulting in a denial of service. The update addresses the vulnerability by correcting how Windows DNS processes queries.
Overview
6.5
CVSS MEDIUM
Important
MS Severity
Not Exploited
MS Exploit Status
Less Likely
MS Exploit Likelihood
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C
ATTACK VECTOR
Network
ATTACK COMPLEXITY
Low
PRIVILEGES REQUIRED
Low
USER INTERACTION
None
SCOPE
Unchanged
CONFIDENTIALITY
None
INTEGRITY
None
AVAILABILITY
High
EXPLOIT CODE MATURITY
Proof-of-Concept
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 5.9
EPSS Score
0.05241
probability of exploitation in the next 30 days
0.91461 percentile - updated 2026-06-21
View on FIRST.org
Affected Products
27 affected products
| Product | KB Article | Severity | Impact | Restart Required |
|---|---|---|---|---|
| Windows 10 for 32-bit Systems | 4550930 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 for x64-based Systems | 4550930 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1607 for 32-bit Systems | 4550929 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1607 for x64-based Systems | 4550929 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1709 for 32-bit Systems | 4550927 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1709 for ARM64-based Systems | 4550927 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1709 for x64-based Systems | 4550927 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1803 for 32-bit Systems | 4550922 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1803 for ARM64-based Systems | 4550922 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1803 for x64-based Systems | 4550922 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1809 for 32-bit Systems | 4549949 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1809 for ARM64-based Systems | 4549949 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1809 for x64-based Systems | 4549949 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1903 for 32-bit Systems | 4549951 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1903 for ARM64-based Systems | 4549951 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1903 for x64-based Systems | 4549951 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1909 for 32-bit Systems | 4549951 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1909 for ARM64-based Systems | 4549951 (Security Update) |
Important | Denial of Service | Yes |
| Windows 10 Version 1909 for x64-based Systems | 4549951 (Security Update) |
Important | Denial of Service | Yes |
| Windows 7 for 32-bit Systems Service Pack 1 4550964 (Monthly Rollup) 4550965 (Security Only) Important Denial of Service 4540688 Base: 6.5 Temporal: 5.9 Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes 4550964 4550965 Windows 7 for x64-based Systems Service Pack 1 4550964 (Monthly Rollup) 4550965 (Security Only) Important Denial of Service 4540688 Base: 6.5 Temporal: 5.9 Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes 4550964 4550965 Windows 8.1 for 32-bit systems 4550961 (Monthly Rollup) 4550970 (Security Only) Important Denial of Service 4541509 Base: 6.5 Temporal: 5.9 Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes 4550961 4550970 Windows 8.1 for x64-based systems 4550961 (Monthly Rollup) 4550970 (Security Only) Important Denial of Service 4541509 Base: 6.5 Temporal: 5.9 Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes 4550961 4550970 Windows RT 8.1 | 4550961 (Monthly Rollup) |
Important | Denial of Service | Yes |
| Windows Server 2008 R2 for x64-based Systems Service Pack 1 4550964 (Monthly Rollup) 4550965 (Security Only) Important Denial of Service 4540688 Base: 6.5 Temporal: 5.9 Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes 4550964 4550965 Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation) 4550964 (Monthly Rollup) 4550965 (Security Only) Important Denial of Service 4540688 Base: 6.5 Temporal: 5.9 Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes 4550964 4550965 Windows Server 2012 4550917 (Monthly Rollup) 4550971 (Security Only) Important Denial of Service 4541510 Base: 6.5 Temporal: 5.9 Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes 4550917 4550971 Windows Server 2012 (Server Core installation) 4550917 (Monthly Rollup) 4550971 (Security Only) Important Denial of Service 4541510 Base: 6.5 Temporal: 5.9 Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes 4550917 4550971 Windows Server 2012 R2 4550961 (Monthly Rollup) 4550970 (Security Only) Important Denial of Service 4541509 Base: 6.5 Temporal: 5.9 Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes 4550961 4550970 Windows Server 2012 R2 (Server Core installation) 4550961 (Monthly Rollup) 4550970 (Security Only) Important Denial of Service 4541509 Base: 6.5 Temporal: 5.9 Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes 4550961 4550970 Windows Server 2016 | 4550929 (Security Update) |
Important | Denial of Service | Yes |
| Windows Server 2016 (Server Core installation) | 4550929 (Security Update) |
Important | Denial of Service | Yes |
| Windows Server 2019 | 4549949 (Security Update) |
Important | Denial of Service | Yes |
| Windows Server 2019 (Server Core installation) | 4549949 (Security Update) |
Important | Denial of Service | Yes |
| Windows Server, version 1803 (Server Core Installation) | 4550922 (Security Update) |
Important | Denial of Service | Yes |
| Windows Server, version 1903 (Server Core installation) | 4549951 (Security Update) |
Important | Denial of Service | Yes |
| Windows Server, version 1909 (Server Core installation) | 4549951 (Security Update) |
Important | Denial of Service | Yes |
Patches
7 patches
| Article | Type | Restart |
|---|---|---|
4550930 |
Security Update | Yes |
4550929 |
Security Update | Yes |
4550927 |
Security Update | Yes |
4550922 |
Security Update | Yes |
4549949 |
Security Update | Yes |
4549951 |
Security Update | Yes |
4550961 |
Monthly Rollup | Yes |
Known Exploits
No known exploits have been linked for this CVE yet. When available, exploit references will be sourced from public repositories and may be unverified, incomplete, or non-functional. Always review code carefully before use in any environment.
Acknowledgments
Quan Luo from Codesafe Team of Legendsec at Qi'anxin Group
References
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