CVEs / CVE-2026-21513
CVE-2026-21513: Microsoft MSHTML Framework Protection Mechanism Failure Vulnerability
- Known exploited in the CISA KEV catalog since 10 Feb 2026
- high 8.8 CVSS 3.1 (from the CNA)
- EPSS 15.8% chance of exploitation in the next 30 days, higher than 96% of CVEs (30 Oct 2026)
- Last changed at its sources
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Summary
Microsoft MSHTML Framework contains a protection mechanism failure vulnerability that could allow an unauthorized attacker to bypass a security feature over a network.
Description
Protection mechanism failure in MSHTML Framework allows an unauthorized attacker to bypass a security feature over a network.
Affected and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| Microsoft Windows 10 Version 1607 | from 10.0.14393.0, before 10.0.14393.8868 | 10.0.14393.8868 |
| Microsoft Windows 10 Version 1809 | from 10.0.17763.0, before 10.0.17763.8389 | 10.0.17763.8389 |
| Microsoft Windows 10 Version 21H2 | from 10.0.19044.0, before 10.0.19044.6937 | 10.0.19044.6937 |
| Microsoft Windows 10 Version 22H2 | from 10.0.19045.0, before 10.0.19045.6937 | 10.0.19045.6937 |
| Microsoft Windows 11 version 22H3 | from 10.0.22631.0, before 10.0.22631.6649 | 10.0.22631.6649 |
| Microsoft Windows 11 Version 23H2 | from 10.0.22631.0, before 10.0.22631.6649 | 10.0.22631.6649 |
| Microsoft Windows 11 Version 24H2 | from 10.0.26100.0, before 10.0.26100.7840 | 10.0.26100.7840 |
| Microsoft Windows 11 Version 25H2 | from 10.0.26200.0, before 10.0.26200.7840 | 10.0.26200.7840 |
| Microsoft Windows 11 version 26H1 | from 10.0.28000.0, before 10.0.28000.1575 | 10.0.28000.1575 |
| Microsoft Windows 11 Version 26H1 | from 10.0.28000.0, before 10.0.28000.1575 | 10.0.28000.1575 |
| Microsoft Windows Server 2012 | from 6.2.9200.0, before 6.2.9200.25923 | 6.2.9200.25923 |
| Microsoft Windows Server 2012 (Server Core installation) | from 6.2.9200.0, before 6.2.9200.25923 | 6.2.9200.25923 |
| Microsoft Windows Server 2012 R2 | from 6.3.9600.0, before 6.3.9600.23022 | 6.3.9600.23022 |
| Microsoft Windows Server 2012 R2 (Server Core installation) | from 6.3.9600.0, before 6.3.9600.23022 | 6.3.9600.23022 |
| Microsoft Windows Server 2016 | from 10.0.14393.0, before 10.0.14393.8868 | 10.0.14393.8868 |
| Microsoft Windows Server 2016 (Server Core installation) | from 10.0.14393.0, before 10.0.14393.8868 | 10.0.14393.8868 |
| Microsoft Windows Server 2019 | from 10.0.17763.0, before 10.0.17763.8389 | 10.0.17763.8389 |
| Microsoft Windows Server 2019 (Server Core installation) | from 10.0.17763.0, before 10.0.17763.8389 | 10.0.17763.8389 |
| Microsoft Windows Server 2022 | from 10.0.20348.0, before 10.0.20348.4773 | 10.0.20348.4773 |
| Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) | from 10.0.25398.0, before 10.0.25398.2149 | 10.0.25398.2149 |
| Microsoft Windows Server 2025 | from 10.0.26100.0, before 10.0.26100.32370 | 10.0.26100.32370 |
| Microsoft Windows Server 2025 (Server Core installation) | from 10.0.26100.0, before 10.0.26100.32370 | 10.0.26100.32370 |
Exploitation
| In CISA KEV since | 10 Feb 2026 |
|---|---|
| Due date for US federal agencies | 3 Mar 2026 |
| Used in ransomware campaigns | Unknown |
| Required action | Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. |
Severity
| CVSS 3.1 | 8.8 highCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HScored by the CNA ([email protected]) |
|---|---|
| Weakness | CWE-693 |
References
- CVE-2026-21513 on NVD
- CVE-2026-21513 in the CISA KEV catalog
- https://msrc.microsoft.com/update-guide/advisory/CVE-2026-21513 (cited by CISA)
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21513 Vendor Advisory
- https://www.vicarius.io/vsociety/posts/cve-2026-21513-detection-script-security-feature-bypass-vulnerability-in-mshtml-framework Third Party Advisory
- https://www.vicarius.io/vsociety/posts/cve-2026-21513-mitigation-script-security-feature-bypass-vulnerability-in-mshtml-framework Mitigation, Third Party Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21513 US Government Resource
Sources
Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.
This product uses data from the NVD API but is not endorsed or certified by the NVD.