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CVE-2026-21513

MSHTML Framework Security Feature Bypass Vulnerability

CVSS 3.1 High 8.8Known exploited (CISA KEV)

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

Description

Protection mechanism failure in MSHTML Framework allows an unauthorized attacker to bypass a security feature over a network.

Official description from the CVE record, published by microsoft. Copyright © 1999-2026 The MITRE Corporation. See /security/cve/legal for the CVE license. View the record on cve.org

Key data

CVSS 3.1 High 8.8

Score published by microsoft in the CVE record.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

  • Attack vector: Network

    The vulnerable component can be reached over a network, possibly from the Internet.

  • Attack complexity: Low

    No special conditions are needed. The attack can be repeated at will.

  • Privileges required: None

    No account or privileges are needed.

  • User interaction: Required

    A user has to do something first, such as opening a file or following a link.

  • Scope: Unchanged

    The impact stays within the vulnerable component.

  • Confidentiality impact: High

    Serious or total effect on the secrecy of data.

  • Integrity impact: High

    Serious or total effect on the trustworthiness of data.

  • Availability impact: High

    Serious or total effect on availability.

CVSS is owned and managed by FIRST.Org, Inc. (FIRST) and is used by permission. Each CVSS score on this site is shown together with its vector string, as published in the CVE record by the source named next to it. Learn more at first.org/cvss.

EPSS

Exploit Prediction Scoring System by FIRST: an estimate of the probability that exploitation activity will be observed in the next 30 days.
Score
0.15852 (15.9% probability)
Percentile
96.9%
Scores of
Nov 10, 2026
Model
v2026.06.15

CISA Known Exploited Vulnerabilities

This CVE is listed in the CISA KEV catalog.
Name in the catalog
Microsoft MSHTML Framework Protection Mechanism Failure Vulnerability
Added to the catalog
Feb 10, 2026
Federal due date
Mar 3, 2026

CISA assessment as of Feb 11, 2026

Stakeholder-Specific Vulnerability Categorization (SSVC) decision points added by CISA.
Exploitation
Recorded by CISA as active
Automatable
no
Technical impact
total

Weakness (CWE)

CWE catalog version 5.0.
CWE names: Copyright © 2006-2026, The MITRE Corporation. See /security/cve/legal for the CWE license.
  • CWE-693Protection Mechanism Failure

Affected products

Products listed in the CVE record, as the CNA published them.

  • Microsoft Windows 10 Version 1607

    • affected: 10.0.14393.0 up to before 10.0.14393.8868

  • Microsoft Windows 10 Version 1809

    • affected: 10.0.17763.0 up to before 10.0.17763.8389

  • Microsoft Windows 10 Version 21H2

    • affected: 10.0.19044.0 up to before 10.0.19044.6937

  • Microsoft Windows 10 Version 22H2

    • affected: 10.0.19045.0 up to before 10.0.19045.6937

  • Microsoft Windows 11 version 22H3

    • affected: 10.0.22631.0 up to before 10.0.22631.6649

  • Microsoft Windows 11 Version 23H2

    • affected: 10.0.22631.0 up to before 10.0.22631.6649

  • Microsoft Windows 11 Version 24H2

    • affected: 10.0.26100.0 up to before 10.0.26100.7840

  • Microsoft Windows 11 Version 25H2

    • affected: 10.0.26200.0 up to before 10.0.26200.7840

  • Microsoft Windows 11 version 26H1

    • affected: 10.0.28000.0 up to before 10.0.28000.1575

  • Microsoft Windows 11 Version 26H1

    • affected: 10.0.28000.0 up to before 10.0.28000.1575

  • Microsoft Windows Server 2012

    • affected: 6.2.9200.0 up to before 6.2.9200.25923

  • Microsoft Windows Server 2012 (Server Core installation)

    • affected: 6.2.9200.0 up to before 6.2.9200.25923

  • Microsoft Windows Server 2012 R2

    • affected: 6.3.9600.0 up to before 6.3.9600.23022

  • Microsoft Windows Server 2012 R2 (Server Core installation)

    • affected: 6.3.9600.0 up to before 6.3.9600.23022

  • Microsoft Windows Server 2016

    • affected: 10.0.14393.0 up to before 10.0.14393.8868

  • Microsoft Windows Server 2016 (Server Core installation)

    • affected: 10.0.14393.0 up to before 10.0.14393.8868

  • Microsoft Windows Server 2019

    • affected: 10.0.17763.0 up to before 10.0.17763.8389

  • Microsoft Windows Server 2019 (Server Core installation)

    • affected: 10.0.17763.0 up to before 10.0.17763.8389

  • Microsoft Windows Server 2022

    • affected: 10.0.20348.0 up to before 10.0.20348.4773

  • Microsoft Windows Server 2022, 23H2 Edition (Server Core installation)

    • affected: 10.0.25398.0 up to before 10.0.25398.2149

  • Microsoft Windows Server 2025

    • affected: 10.0.26100.0 up to before 10.0.26100.32370

  • Microsoft Windows Server 2025 (Server Core installation)

    • affected: 10.0.26100.0 up to before 10.0.26100.32370

References

Links listed in the CVE record. They lead to other sites, which CubePath does not control.

Timeline

  1. ID reserved
  2. Added to CISA KEV
  3. Record published
  4. Record last updated

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Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 19:12 UTC. Sources and licenses