CVE-2026-42915

Microsoft Windows 10 21H2 ≤ 10.0.19044.7417

Published

09 June 2026

Modified

19 June 2026

Patch / advisory

View advisory

CVSS Score v3.1 5.5

Click a component to see what it means

Raw vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS Score 0.0038 31th percentile

Risk Priority 44 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2026-42915 is a medium-severity Incorrect Calculation of Buffer Size (CWE-131) vulnerability in Microsoft Windows 10 21H2. Its CVSS base score is 5.5 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 31th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.

EU & UK References

🇪🇺 ENISA EUVD: EUVD-2026-35727

Vulnerability Data

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

CWE(s): CWE-131

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation

Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.

attack.mitre.org →

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1203 Exploitation for Client Execution Execution

Adversaries may exploit software vulnerabilities in client applications to execute code.

attack.mitre.org →

T1210 Exploitation of Remote Services Lateral Movement

Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.

attack.mitre.org →

T1212 Exploitation for Credential Access Credential Access

Adversaries may exploit software vulnerabilities in an attempt to collect credentials.

attack.mitre.org →

Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2024-43631Same product: Microsoft Windows 10 21H2

CVE-2024-43630Same product: Microsoft Windows 10 21H2

CVE-2020-17087Same vendor: Microsoft

CVE-2024-43629Same product: Microsoft Windows 10 21H2

CVE-2024-43624Same product: Microsoft Windows 10 21H2

CVE-2024-38150Same product: Microsoft Windows 10 21H2

CVE-2024-38246Same product: Microsoft Windows 10 21H2

CVE-2024-43529Same product: Microsoft Windows 10 21H2

CVE-2024-38248Same product: Microsoft Windows 10 21H2

CVE-2024-43574Same product: Microsoft Windows 10 21H2

Affected Assets

microsoft

windows 10 21h2

≤ 10.0.19044.7417 · ≤ 10.0.19044.7417 · ≤ 10.0.19044.7417

microsoft

windows 10 22h2

≤ 10.0.19045.7417 · ≤ 10.0.19045.7417 · ≤ 10.0.19045.7417

microsoft

windows 11 23h2

≤ 10.0.22631.7219 · ≤ 10.0.22631.7219

microsoft

windows 11 24h2

≤ 10.0.26100.8655 · ≤ 10.0.26100.8655

microsoft

windows 11 25h2

≤ 10.0.26200.8655 · ≤ 10.0.26200.8655

microsoft

windows 11 26h1

≤ 10.0.28000.2269 · ≤ 10.0.28000.2269

microsoft

windows server 2022

≤ 10.0.20348.5256

microsoft

windows server 2025

≤ 10.0.26100.32995

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer security testing and code review can discover incorrect buffer-size computations before deployment.

SA-8 Security and Privacy Engineering Principles partial match

Secure engineering principles directly require correct buffer-size arithmetic and bounds-checked allocation.

SI-10 Information Input Validation partial match

Input validation can enforce that supplied lengths or counts used in size calculations are within safe bounds.

SI-16 Memory Protection partial match

Memory-protection mechanisms limit the exploitability of an overflow that results from an incorrect size calculation.

SI-2 Flaw Remediation partial match

Flaw-remediation processes that include vulnerability scanning or static analysis will surface buffer-size errors.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match

prevents

Secure SDLC practices directly prevent buffer-size miscalculations via coding standards, reviews, and testing, while fixing this single weakness only partially fulfills the broader control.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.28 Secure coding mostly match

degrades

Secure coding standards directly require correct buffer-size calculations.

A.8.29 Security testing in development and acceptance mostly match

finds

Security testing can detect buffer-size errors before release.

A.8.25 Secure development life cycle partial match

prevents

Secure development lifecycle mandates size-checking practices that reduce buffer-size miscalculations.

A.8.26 Application security requirements partial match

prevents

Application security requirements can specify buffer-size validation rules.