What is the CVSS score of CVE-2026-20817?

CVE-2026-20817 has a CVSS 3.1 base score of 7.8 (High). CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.0%.

Is there a public PoC exploit available for CVE-2026-20817?

Yes, a public proof-of-concept exploit is available for CVE-2026-20817. Prioritise patching immediately. EPSS: 0.0%.

How to fix or mitigate CVE-2026-20817?

Within 7 days: Identify all affected systems and apply vendor patches promptly. Monitor vendor channels for patch availability.

Windows 10 21h2 CVE-2026-20817

HIGH

Improper Handling of Insufficient Permissions or Privileges (CWE-280)

2026-01-13 secure@microsoft.com

Information Disclosure Microsoft Windows 10 21h2 Windows 10 22h2 Windows 11 23h2 Windows 11 24h2 Windows 11 25h2 Windows Server 2022 Windows Server 2022 23h2 Windows Server 2025

7.8

CVSS 3.1 · Vendor: microsoft

View

Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

Access

Authenticate as low-privilege user
Exploit

Access Windows Error Reporting service
Execution

Exploit insufficient permission checks
Impact

Escalate to SYSTEM privileges

Vulnerability Assessment

Weakness	CWE CWE-280 OWASP Top 10:2025 A10:2025 - Mishandling of Exceptional Conditions ASVS 5.0 V8 - Authorization Insufficient permission handling
Exploitation Conditions	Local user account required on Windows system with Windows Error Reporting service enabled. Attacker must have valid logon credentials (PR:L). Standard Windows configurations with default Error Reporting enabled are vulnerable.
Impact	CVSS 7.8 (HIGH). Attack vector: Local. Complexity: Low. Privileges required: Low. User interaction: None. Exploitable via local access.
Exploit ScenarioDerived	An attacker could exploit this vulnerability to compromise the affected system.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 12, 2026

Windows Error Reporting on Windows 10, Windows 11, and Windows Server 2022 fails to properly validate user privileges, enabling local authenticated users to escalate to system-level access. An attacker with valid credentials can exploit this permission handling flaw to gain full control over the affected system. Currently no patch is available for this high-severity vulnerability (CVSS 7.8).

Earlier versions of this analysis (1)

v1 Mar 12, 2026 - 21:54 CVSS 7.8

Improper handling of insufficient permissions or privileges in Windows Error Reporting allows an authorized attacker to elevate privileges locally. [CVSS 7.8 HIGH]

RemediationAI

Monitor vendor advisories for a patch.

Affected Packages

microsoft windows_10_version_21h2_10_0_19044_6809 fix: Windows 10 Version 21H2 for 32-bit Systems 10.0.19044.6809, Windows 10 Version 21H2 for ARM64-based Systems 10.0.19044.6809, Windows 10 Version 21H2 for x64-based Systems 10.0.19044.6809

microsoft windows_10_version_22h2_10_0_19045_6809 fix: Windows 10 Version 22H2 for 32-bit Systems 10.0.19045.6809, Windows 10 Version 22H2 for ARM64-based Systems 10.0.19045.6809, Windows 10 Version 22H2 for x64-based Systems 10.0.19045.6809

microsoft windows_11_version_23h2_10_0_22631_6491 fix: Windows 11 Version 23H2 for ARM64-based Systems 10.0.22631.6491, Windows 11 Version 23H2 for x64-based Systems 10.0.22631.6491

microsoft windows_11_version_24h2_10_0_26100_7623 fix: Windows 11 Version 24H2 for ARM64-based Systems 10.0.26100.7623, Windows 11 Version 24H2 for x64-based Systems 10.0.26100.7623

microsoft windows_11_version_25h2_10_0_26200_7623 fix: Windows 11 Version 25H2 for ARM64-based Systems 10.0.26200.7623, Windows 11 Version 25H2 for x64-based Systems 10.0.26200.7623

microsoft windows_server_2022_10_0_20348_4648 fix: Windows Server 2022 10.0.20348.4648, Windows Server 2022 (Server Core installation) 10.0.20348.4648

microsoft windows_server_2022_23h2_edition_10_0_25398_2092 fix: Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.2092

microsoft windows_server_2025_10_0_26100_32230 fix: Windows Server 2025 10.0.26100.32230, Windows Server 2025 (Server Core installation) 10.0.26100.32230

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 8 packages in microsoft

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

Affects Windows 10 21H2. Improper handling of insufficient permissions or privileges in Windows Error Reporting allows an authorized attacker to elevate privileges locally.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (microsoft) PRIMARY 7.8 HIGH

AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

ENISA EUVD HIGH

Primary rating from Vendor (microsoft).

CVSS VectorVendor: microsoft

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

DescriptionCVE.org

Improper handling of insufficient permissions or privileges in Windows Error Reporting allows an authorized attacker to elevate privileges locally.

Executive ViewAI

Why It Matters

CVE-2026-20817 presents notable security risk rated CVSS 7.8. Exploitation could compromise the security of affected deployments. Organizations should apply vendor updates when available and consider compensating controls in the interim.

Business Impact: High

Compensating Controls

Apply vendor patch. If immediate patching is not feasible: (1) Implement network-level access controls to limit exposure; (2) Enable enhanced monitoring and alerting; (3) Apply principle of least privilege.

Threat Intelligence Overview

EPSS Score

0.0%

Top 95% exploitable

Threat Intel

1 source

Exploit

POC

Public exploit code exists

Data Quality

5 sources

Confidence: Medium

NVD

CVE.org

EPSS NCSC-NL

VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC Yes

EPSS 0.0%

Patch available Yes

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

Poc

System Exposure· derived

Small

Automatable· derived

Human Impact

High

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +39

PoC: +20

Weaponized: 0

Threat intel: 0

Gov advisory: +5

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.