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Full vulnerability report · 2020
CVE-2020-1118High confidence

Microsoft Windows Transport Layer Security Denial of Service Vulnerability

Microsoft · Windows 10 Version 1709

8.6HighCVSS 3.1
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:Critical, raised one band.upgradedsince 5 Oct 2026

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 14.68% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Microsoft Windows 10 Version 1709 and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2020-12005

No EUVD known-exploited evidence

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.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
8.6 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

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.

What

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.

Why

The current structured CVE record identifies a security weakness, but the root cause requires confirmation in the linked vendor material.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

What

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.

Why

The current structured CVE record identifies a security weakness, but the root cause requires confirmation in the linked vendor material.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → vulnerable operation → disrupt the affected service
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Changed: exploitation can affect a different security authority
Weakness
?CWE means Common Weakness Enumeration.
CWE not yet assigned
CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:P/RL:O/RC:C

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SChangedScope: The attack can affect a component governed by a different security authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedDenial of service
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2020-12005Official EUVD mapping

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.

Official EUVD record ↗
Cyber Security Agency of Singapore · English · CSA-SB-20200527Security Bulletin 27 May 2020

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 27 May 2020, published on 27 May 2020. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2020-AVI-287Multiples vulnérabilités dans Microsoft Windows

.cve.org/CVERecord?id=CVE-2020-1090 Référence CVE CVE-2020-1109 https://www.cve.org/CVERecord?id=CVE-2020-1109 Référence CVE CVE-2020-1110 https://www.cve.org/CVERecord?id=CVE-2020-1110 Référence CVE CVE-2020-1111 https://www.cve.org/CVERecord?id=CVE-2020-1111 Référence CVE CVE-2020-1112 https://www.cve.org/CVERecord?id=CVE-2020-1112 Référence CVE CVE-2020-1113 https://www.cve.org/CVERecord?id=CVE-2020-1113 Référence CVE CVE-2020-1114 https://www.cve.org/CVERecord?id=CVE-2020-1114 Référence CVE CVE-2020-1116 https://www.cve.org/CVERecord?id=CVE-2020-1116 Référence CVE CVE-2020-1117 https://www.cve.org/CVERecord?id=CVE-2020-1117 Référence CVE CVE-2020-1118 https://www.cve.org/CVERecord?id=CVE-2020-1118 Référence CVE CVE-2020-1121 https://www.cve.org/CVERecord?id=CVE-2020-1121 Référence CVE CVE-2020-1123 https://www.cve.org/CVERecord?id=CVE-2020-1123 Référence CVE CVE-2020-1124 https://www.cve.org/CVERecord?id=CVE-2020-1124 Référence CVE CVE-2020-1125 https://www.cve.org/CVERecord?id=CVE-2020-1125 Référence CVE CVE-2020-1126 https://www.cve.org/CVERecord?id=CVE-2020-1126 Référence CVE CVE-2020-1131 https://www.cve.org/CVERecord?id=CVE-2020-1131 Référence CVE CVE-2020-1132 https://www.cve.org/CVERecord?id=CVE-2020-1132 Référence CVE CVE-2020-1134 https://www.cve.org/CVERecord?id=CVE-2020-1134 Ré

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2020-005773複数の Microsoft Windows 製品におけるサービス運用妨害 (DoS) の脆弱性

Microsoft Windows 10、Windows Server 2019、Windows Server には、Windows のトランスポート層セキュリティ (TLS) の実装で特定のキー交換が適切に処理されない場合、サービス運用妨害 (DoS) の脆弱性が存在します。 ベンダは、本脆弱性を「Microsoft Windows トランスポート層セキュリティのサービス拒否の脆弱性」として公開しています。

Official advisory ↗
KISA KrCERT/CC · Korean · KNVD-5139MS 5월 보안 위협에 따른 정기 보안 업데이트 권고

- 서비스거부 취약점(CVE-2020-0909, CVE-2020-1076, CVE-2020-1084, CVE-2020-1118, CVE-2020-1123)

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
Fixed
An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 21 May 2020 · Last source change 19 Aug 2026, 16:33 UTC · CWE not yet assigned

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2020-12005
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceUnavailable
NVD statusNVD modified after enrichment

Missing structured fields: CWE classification. Missing data is not evidence of low risk; review the primary advisory.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Vendor guidanceAuthoritative vendor guidance changed: added remediation: portal.msrc.microsoft.com/CVE-2020-1118; removed patch: msrc.microsoft.com/CVE-2020-1118; removed remediation: msrc.microsoft.com/CVE-2020-1118.
    Before
    patch: msrc.microsoft.com/CVE-2020-1118 · patch: portal.msrc.microsoft.com/CVE-2020-1118 · remediation: msrc.microsoft.com/CVE-2020-1118
    After
    patch: portal.msrc.microsoft.com/CVE-2020-1118 · remediation: portal.msrc.microsoft.com/CVE-2020-1118
    portal.msrc.microsoft.com ↗
  2. Vendor guidanceAuthoritative vendor guidance changed: added patch: msrc.microsoft.com/CVE-2020-1118; added remediation: msrc.microsoft.com/CVE-2020-1118; removed remediation: portal.msrc.microsoft.com/CVE-2020-1118.
    Before
    patch: portal.msrc.microsoft.com/CVE-2020-1118 · remediation: portal.msrc.microsoft.com/CVE-2020-1118
    After
    patch: msrc.microsoft.com/CVE-2020-1118 · patch: portal.msrc.microsoft.com/CVE-2020-1118 · remediation: msrc.microsoft.com/CVE-2020-1118
    msrc.microsoft.com ↗
  3. Affected versionsThe structured affected or fixed version information changed.
    Before
    10 Version 1803 for 32-bit Systems; 10 Version 1803 for x64-based Systems; 10 Version 1803 for ARM64-based Systems; 10 Version 1809 for 32-bit Systems; 10 Version 1809 for x64-based Systems; 10 Version 1809 for ARM64-based Systems; 10 Version 1709 for 32-bit Systems; 10 Version 1709 for x64-based Systems · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    After
    10.0.0 < publication; 10.0.17763.0 < publication · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    CNA ↗
  4. CVSS scoreCVSS score changed from 7.5 (CVSS 3.1 · NIST NVD · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) to 8.6 (CVSS 3.1 · CNA · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:P/RL:O/RC:C).
    Before
    7.5 (CVSS 3.1 · NIST NVD · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
    After
    8.6 (CVSS 3.1 · CNA · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:P/RL:O/RC:C)
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2020-12005↗Patch or update reference↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2020-1118 · cve.blacktree.nl