Cyber Resilience

CVE-2026-40406

Memory Safety in Microsoft Windows 10 21H2 ≤ 10.0.19044.7291

Memory Safety
Published
12 May 2026
Modified
17 June 2026
Patch / advisory
View advisory
CVSS Score v3.1 7.5
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS Score 0.0093 57th percentile
Risk Priority 55 floored blend · peak EPSS

Summary

CVE-2026-40406 is a high-severity Use After Free (CWE-416) vulnerability in Microsoft Windows 10 21H2. Its CVSS base score is 7.5 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Credential Access (T1212); ranked in the top 43% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SI-16 (Memory Protection) and SI-2 (Flaw Remediation) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

Use after free in Windows TCP/IP allows an unauthorized attacker to disclose information over a network.

CWE(s)
CWE-416

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
T1005 Data from Local System Collection
Adversaries may search local system sources, such as file systems, configuration files, local databases, virtual machine files, or process memory, to find files of interest and sensitive data prior to Exfiltration.
attack.mitre.org →
Why these techniques?

Remote unauthenticated use-after-free in the TCP/IP stack directly enables exploitation for information disclosure (T1212) and remote retrieval of local system data (T1005).

Confidence: MEDIUM · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2026-27925Same product: Microsoft Windows 10 1607
CVE-2026-27916Same product: Microsoft Windows 10 1607
CVE-2026-42825Same product: Microsoft Windows 10 1607
CVE-2026-27922Same product: Microsoft Windows 10 1607
CVE-2026-27923Same product: Microsoft Windows 10 1607
CVE-2026-34338Same product: Microsoft Windows 10 1607
CVE-2026-35416Same product: Microsoft Windows 10 1607
CVE-2026-34347Same product: Microsoft Windows 10 1607
CVE-2026-23669Same product: Microsoft Windows 10 1607
CVE-2026-27915Same product: Microsoft Windows 10 1607

Affected Assets

microsoft
windows 10 1607
≤ 10.0.14393.9140 · ≤ 10.0.14393.9140
microsoft
windows 10 1809
≤ 10.0.17763.8755 · ≤ 10.0.17763.8755
microsoft
windows 10 21h2
≤ 10.0.19044.7291 · ≤ 10.0.19044.7291 · ≤ 10.0.19044.7291
microsoft
windows 10 22h2
≤ 10.0.19045.7291 · ≤ 10.0.19045.7291 · ≤ 10.0.19045.7291
microsoft
windows 11 23h2
≤ 10.0.22631.7079 · ≤ 10.0.22631.7079
microsoft
windows 11 24h2
≤ 10.0.26100.8390 · ≤ 10.0.26100.8390
microsoft
windows 11 25h2
≤ 10.0.26200.8390 · ≤ 10.0.26200.8390
microsoft
windows 11 26h1
≤ 10.0.28000.2113 · ≤ 10.0.28000.2113
microsoft
windows server 2012
all versions, r2
microsoft
windows server 2016
≤ 10.0.14393.9140
+4 more product configuration(s) — see NVD for full list

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)
  • SI-16 Memory Protection
  • SI-2 Flaw Remediation
  • SC-7 Boundary Protection
Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 3 hardening rules · 3 OS baselines
Validate
Prove the fix (OWASP ASVS)
  • V1.4.3

Mitigating Controls (NIST 800-53 r5) AI

SI-16 Memory Protection good match
prevent

Directly enforces memory safety mechanisms that block use-after-free exploitation in the TCP/IP stack.

SI-2 Flaw Remediation good match
prevent

Requires timely patching of the identified use-after-free flaw in Windows TCP/IP before it can be exploited for disclosure.

SC-7 Boundary Protection partial match
prevent

Boundary filtering and network segmentation limit an attacker's ability to send crafted packets that trigger the remote UAF condition.

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 incorporate memory-safety tooling and reviews that prevent most use-after-free defects.

ID.RA-01 partial match
prevents

Vulnerability identification processes can discover use-after-free issues via scanning or analysis but do not prevent their introduction.

PR.PS-02 partial match
prevents

Routine patching removes known use-after-free instances after they have been introduced in released software.

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
detects

Security testing in development can detect use-after-free bugs before release.

A.8.25 Secure development life cycle partial match
prevents

Secure SDLC mandates memory-safety practices that reduce use-after-free defects.

A.8.26 Application security requirements partial match
prevents

Application security requirements can specify memory-management rules that mitigate use-after-free.

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

Secure architecture principles include memory-safety design choices that limit use-after-free exposure.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly prescribe avoidance of use-after-free patterns.

A.8.32 Change management partial match
prevents

Change-management processes help ensure memory-safety fixes are deployed consistently.

References