How severe is CVE-2026-20810?

CVE-2026-20810 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-2026-20810 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (38th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-20810?

CVE-2026-20810 primarily affects Microsoft Windows 10 1809. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-20810?

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-2026-20810 have an EU (EUVD) identifier?

Yes. CVE-2026-20810 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-2194.

When was CVE-2026-20810 published?

CVE-2026-20810 was published on 2026-01-13 and last updated on 2026-06-17.

CVE-2026-20810

CVE-2026-20810 is a high-severity vulnerability in Microsoft Windows 10 1809 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-590.

Key facts

Severity: High (CVSS 3.x base score 7.8)
EPSS exploit prediction: 0% (38th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-2194
Weakness: CWE-590
Affected product: Microsoft Windows 10 1809
Published: 2026-01-13
Last modified: 2026-06-17

Description

Free of memory not on the heap in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

Frequently asked questions

What is CVE-2026-20810?: Free of memory not on the heap in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.
How severe is CVE-2026-20810?: CVE-2026-20810 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-2026-20810 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (38th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-20810?: CVE-2026-20810 primarily affects Microsoft Windows 10 1809. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-20810?: 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-2026-20810 have an EU (EUVD) identifier?: Yes. CVE-2026-20810 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-2194.
When was CVE-2026-20810 published?: CVE-2026-20810 was published on 2026-01-13 and last updated on 2026-06-17.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20810

Affected products (5)

cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x86:*
cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:*

More vulnerabilities in Microsoft Windows 10 1809

CVE-2025-49708 — Critical (CVSS 9.9): Use after free in Microsoft Graphics Component allows an authorized attacker to elevate privileges over a network.
CVE-2026-47291 — Critical (CVSS 9.8): Integer overflow or wraparound in Windows HTTP.sys allows an unauthorized attacker to execute code over a network.
CVE-2026-44815 — Critical (CVSS 9.8): Stack-based buffer overflow in Windows DHCP Client allows an unauthorized attacker to execute code over a network.
CVE-2026-33824 — Critical (CVSS 9.8): Double free in Windows IKE Extension allows an unauthorized attacker to execute code over a network.
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CVE-2025-53766 — Critical (CVSS 9.8): Heap-based buffer overflow in Windows GDI+ allows an unauthorized attacker to execute code over a network.

All CVEs affecting Microsoft Windows 10 1809 →

Other CWE-590 vulnerabilities

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CVE-2025-54899 — High (CVSS 7.8): Free of memory not on the heap in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
CVE-2025-42995 — High (CVSS 7.5): SAP MDM Server Read function allows an attacker to send specially crafted packets which could trigger a memory read…
CVE-2025-42994 — High (CVSS 7.5): SAP MDM Server ReadString function allows an attacker to send specially crafted packets which could trigger a memory…
CVE-2023-22291 — High (CVSS 7.0): An invalid free vulnerability exists in the Frame stream parser functionality of Ichitaro 2022 1.0.1.57600. A specially…
CVE-2026-47328 — Medium (CVSS 6.1): Ubuntu Linux 6.8, 6.17 and 7.0 contain AppArmor SAUCE patches which incorrectly attempt to free a pointer which was not…

Browse all CWE-590 vulnerabilities →