How severe is CVE-2026-21245?

CVE-2026-21245 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-2026-21245 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (34th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-21245?

CVE-2026-21245 primarily affects Microsoft Windows 11 24h2. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-21245?

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-2026-21245 have an EU (EUVD) identifier?

Yes. CVE-2026-21245 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-7322.

When was CVE-2026-21245 published?

CVE-2026-21245 was published on 2026-02-10 and last updated on 2026-06-17.

CVE-2026-21245

CVE-2026-21245 is a high-severity vulnerability in Microsoft Windows 11 24h2 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-787.

Key facts

Severity: High (CVSS 3.x base score 7.8)
EPSS exploit prediction: 0% (34th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-7322
Weakness: CWE-787
Affected product: Microsoft Windows 11 24h2
Published: 2026-02-10
Last modified: 2026-06-17

Description

Heap-based buffer overflow in Windows Kernel allows an authorized attacker to elevate privileges locally.

Frequently asked questions

What is CVE-2026-21245?: Heap-based buffer overflow in Windows Kernel allows an authorized attacker to elevate privileges locally.
How severe is CVE-2026-21245?: CVE-2026-21245 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-2026-21245 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (34th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-21245?: CVE-2026-21245 primarily affects Microsoft Windows 11 24h2. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-21245?: 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-2026-21245 have an EU (EUVD) identifier?: Yes. CVE-2026-21245 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-7322.
When was CVE-2026-21245 published?: CVE-2026-21245 was published on 2026-02-10 and last updated on 2026-06-17.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21245

Affected products (5)

cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:*:*

More vulnerabilities in Microsoft Windows 11 24h2

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-2026-45657 — Critical (CVSS 9.8): Use after free in Windows Kernel 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-2026-41096 — Critical (CVSS 9.8): Heap-based buffer overflow in Microsoft Windows DNS 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.

All CVEs affecting Microsoft Windows 11 24h2 →

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