Cyber Resilience

CVE-2026-40409

Microsoft Windows 10 21H2 ≤ 10.0.19044.7417

Published
09 June 2026
Modified
17 June 2026
Patch / advisory
View advisory
CVSS Score v3.1 7.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.0030 22th percentile
Risk Priority 56 floored blend · peak EPSS

Summary

CVE-2026-40409 is a high-severity Numeric Truncation Error (CWE-197) vulnerability in Microsoft Windows 10 21H2. Its CVSS base score is 7.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 22th 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-15 (Development Process, Standards, and Tools) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

Windows Universal Disk Format File System Driver (UDFS) Elevation of Privilege Vulnerability

CWE(s)
CWE-197

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-2026-50357Same product: Microsoft Windows 10 1607
CVE-2026-49792Same product: Microsoft Windows 10 1607
CVE-2026-40404Same product: Microsoft Windows 10 1607
CVE-2026-56650Same product: Microsoft Windows 10 1607
CVE-2026-50332Same product: Microsoft Windows 10 1607
CVE-2025-49679Same product: Microsoft Windows 10 1607
CVE-2024-43519Same product: Microsoft Windows 10 1607
CVE-2024-38125Same product: Microsoft Windows 10 1607
CVE-2024-21377Same product: Microsoft Windows 10 1607
CVE-2026-40380Same product: Microsoft Windows 10 1607

Affected Assets

microsoft
windows 10 1607
≤ 10.0.14393.9234 · ≤ 10.0.14393.9234
microsoft
windows 10 1809
≤ 10.0.17763.8880 · ≤ 10.0.17763.8880
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 2012
all versions, r2
microsoft
windows server 2016
≤ 10.0.14393.9234
+3 more product configuration(s) — see NVD for full list

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation can discover truncation errors through static analysis, dynamic testing, or code review.

SA-15 Development Process, Standards, and Tools partial match

Documented development standards and tools can mandate use of safe arithmetic libraries or explicit checks against truncation.

SA-8 Security and Privacy Engineering Principles partial match

Engineering principles can require safe type conversions and avoidance of narrowing casts that cause truncation.

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 truncation errors via reviews, static analysis, and safe type handling.

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.8.29 Security testing in development and acceptance mostly match
finds

Security testing can detect truncation bugs through static analysis and fuzzing.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle mandates practices that can catch numeric truncation during design and code review.

A.8.26 Application security requirements partial match
degrades

Application security requirements can specify safe numeric handling and data-type constraints.

A.8.27 Secure system architecture and engineering principles partial match
degrades

Secure architecture principles include choosing appropriate data types and avoiding unsafe casts.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly prohibit unsafe narrowing conversions and truncation.

References