How severe is CVE-2026-42915?

CVE-2026-42915 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-42915 being actively exploited?

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

What products are affected by CVE-2026-42915?

CVE-2026-42915 primarily affects Microsoft Windows 10 21h2. In total, 16 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-42915?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-42915 have an EU (EUVD) identifier?

Yes. CVE-2026-42915 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-35727.

When was CVE-2026-42915 published?

CVE-2026-42915 was published on 2026-06-09 and last updated on 2026-06-19.

CVE-2026-42915

CVE-2026-42915 is a medium-severity vulnerability in Microsoft Windows 10 21h2 with a CVSS 3.x base score of 5.5. 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-131.

Key facts

Severity: Medium (CVSS 3.x base score 5.5)
EPSS exploit prediction: 0% (30th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-35727
Weakness: CWE-131
Affected product: Microsoft Windows 10 21h2
Published: 2026-06-09
Last modified: 2026-06-19

Description

Incorrect calculation of buffer size in Windows VMSwitch allows an authorized attacker to deny service locally.

Frequently asked questions

What is CVE-2026-42915?: Incorrect calculation of buffer size in Windows VMSwitch allows an authorized attacker to deny service locally.
How severe is CVE-2026-42915?: CVE-2026-42915 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-42915 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (30th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-42915?: CVE-2026-42915 primarily affects Microsoft Windows 10 21h2. In total, 16 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-42915?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-42915 have an EU (EUVD) identifier?: Yes. CVE-2026-42915 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-35727.
When was CVE-2026-42915 published?: CVE-2026-42915 was published on 2026-06-09 and last updated on 2026-06-19.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42915

Affected products (16)

cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:x86:*
cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:x86:*
cpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:x64:*
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_11_26h1:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_11_26h1:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:x64:*

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