CVE-2018-8304 — Windows DNSAPI Denial of Service Vulnerability

Executive Summary

A denial of service vulnerability exists in Windows Domain Name System (DNS) DNSAPI.dll when it fails to properly handle DNS responses. An attacker who successfully exploited the vulnerability could cause a system to stop responding. Note that the denial of service condition would not allow an attacker to execute code or to elevate user privileges. However, the denial of service condition could prevent authorized users from using system resources. To exploit the vulnerability, the attacker would use a malicious DNS server to send corrupted DNS responses to the target. The update addresses the vulnerability by modifying how Windows DNSAPI.dll handles DNS responses.

Overview

5.9

CVSS MEDIUM

Important

MS Severity

Not Exploited

MS Exploit Status

N/A

MS Exploit Likelihood

Category Denial of Service

Released Jul 10 2018

Last Updated Jul 10 2018

Publicly Disclosed No

CISA KEV Not Listed

Known Exploits None Known

EPSS Score 0.11796 — 0.95709 percentile

CVSS Vector

ATTACK VECTOR

Network

ATTACK COMPLEXITY

High

PRIVILEGES REQUIRED

None

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: 5.3

EPSS Score

0.11796

probability of exploitation in the next 30 days

0.95709 percentile - updated 2026-08-14

View on FIRST.org

Affected Products

6 affected products

Product	KB Article	Severity	Impact	Restart Required
Windows 10 for 32-bit Systems 4338829 (Security Update) 4345455 (Alternate Cumulative) Important Denial of Service 4284860 Base: 5.9 Temporal: 5.3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes None Windows 10 for x64-based Systems 4338829 (Security Update) 4345455 (Alternate Cumulative) Important Denial of Service 4284860 Base: 5.9 Temporal: 5.3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes None Windows 10 Version 1607 for 32-bit Systems 4338814 (Security Update) 4345418 (Alternate Cumulative) Important Denial of Service 4284880 Base: 5.9 Temporal: 5.3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes None Windows 10 Version 1607 for x64-based Systems 4338814 (Security Update) 4345418 (Alternate Cumulative) Important Denial of Service 4284880 Base: 5.9 Temporal: 5.3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes None Windows 10 Version 1703 for 32-bit Systems 4338826 (Security Update) 4345419 (Alternate Cumulative) Important Denial of Service 4284874 Base: 5.9 Temporal: 5.3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes None Windows 10 Version 1703 for x64-based Systems 4338826 (Security Update) 4345419 (Alternate Cumulative) Important Denial of Service 4284874 Base: 5.9 Temporal: 5.3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes None Windows 10 Version 1709 for 32-bit Systems 4338825 (Security Update) 4345420 (Alternate Cumulative) Important Denial of Service 4284819 Base: 5.9 Temporal: 5.3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes None Windows 10 Version 1709 for x64-based Systems 4338825 (Security Update) 4345420 (Alternate Cumulative) Important Denial of Service 4284819 Base: 5.9 Temporal: 5.3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes None Windows 7 for 32-bit Systems Service Pack 1 4338818 (Monthly Rollup) 4338823 (Security Only) 4338821 (Preview Rollup) 4345459 (Standalone) Important Denial of Service 4284826 Base: 5.9 Temporal: 5.3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes None Windows 7 for x64-based Systems Service Pack 1 4338818 (Monthly Rollup) 4338823 (Security Only) 4338821 (Preview Rollup) 4345459 (Standalone) Important Denial of Service 4284826 Base: 5.9 Temporal: 5.3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes None Windows 8.1 for 32-bit systems 4338815 (Monthly Rollup) 4338824 (Security Only) 4338831 (Preview Rollup) 4345424 (Standalone) Important Denial of Service 4284815 Base: 5.9 Temporal: 5.3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes None Windows 8.1 for x64-based systems 4338815 (Monthly Rollup) 4338824 (Security Only) 4338831 (Preview Rollup) 4345424 (Standalone) Important Denial of Service 4284815 Base: 5.9 Temporal: 5.3 Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C Yes None Windows RT 8.1	`4338815 (Monthly Rollup)`	Important	Denial of Service	Yes
Windows Server 2008 for 32-bit Systems Service Pack 2	`4291391 (Security Update)`	Important	Denial of Service	Yes
Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation)	`4291391 (Security Update)`	Important	Denial of Service	Yes
Windows Server 2008 for Itanium-Based Systems Service Pack 2	`4291391 (Security Update)`	Important	Denial of Service	Yes
Windows Server 2008 for x64-based Systems Service Pack 2	`4291391 (Security Update)`	Important	Denial of Service	Yes
Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation)	`4291391 (Security Update)`	Important	Denial of Service	Yes

Patches

2 patches

Article	Type	Restart
`4338815`	Monthly Rollup	Yes
`4291391`	Security Update	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

Roberto Rodriguez ( @Cyb3rWard0g
Nick Freeman

References

MSRC Advisory MITRE NVD