How severe is CVE-2026-20817?

CVE-2026-20817 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-20817 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 5% (92nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-20817?

CVE-2026-20817 primarily affects Microsoft Windows 10 21h2. In total, 8 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-20817?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-20817 have an EU (EUVD) identifier?

Yes. CVE-2026-20817 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-2188.

When was CVE-2026-20817 published?

CVE-2026-20817 was published on 2026-01-13 and last updated on 2026-06-17.

CVE-2026-20817

CVE-2026-20817 is a high-severity vulnerability in Microsoft Windows 10 21h2 with a CVSS 3.x base score of 7.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-280.

Key facts

Severity: High (CVSS 3.x base score 7.8)
EPSS exploit prediction: 5% (92nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-2188
Weakness: CWE-280
Affected product: Microsoft Windows 10 21h2
Published: 2026-01-13
Last modified: 2026-06-17

Description

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

Frequently asked questions

What is CVE-2026-20817?: Improper handling of insufficient permissions or privileges in Windows Error Reporting allows an authorized attacker to elevate privileges locally.
How severe is CVE-2026-20817?: CVE-2026-20817 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-20817 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 5% (92nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-20817?: CVE-2026-20817 primarily affects Microsoft Windows 10 21h2. In total, 8 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-20817?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-20817 have an EU (EUVD) identifier?: Yes. CVE-2026-20817 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-2188.
When was CVE-2026-20817 published?: CVE-2026-20817 was published on 2026-01-13 and last updated on 2026-06-17.

References

Affected products (8)

cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2022_23h2:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:*:*

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