CVE-2026-21513
HIGHCISA KEVEPSS 96th pctlDescription
Protection mechanism failure in MSHTML Framework allows an unauthorized attacker to bypass a security feature over a network.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
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
Exploit Intelligence
Very high risk: more likely to be exploited than 96% of all known CVEs.
Microsoft MSHTML Framework Protection Mechanism Failure Vulnerability
Microsoft MSHTML Framework contains a protection mechanism failure vulnerability that could allow an unauthorized attacker to bypass a security feature over a network.
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Remediation due: 2026-03-03
References
Related Vulnerabilities
Other CWE-693 (Protection Mechanism Failure) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2013-2465 | Critical | 9.8 | 99% | KEV + Ransom | - |
| CVE-2024-21412 | High | 8.1 | 95% | KEV + Ransom | Fix |
| CVE-2013-0431 | Medium | 5.3 | 90% | KEV + Ransom | - |
| CVE-2019-1003030 | Critical | 9.9 | 76% | KEV | - |
| CVE-2025-40536 | High | 8.1 | 72% | KEV | Fix |
| CVE-2025-0411 | High | 7.0 | 67% | KEV | Fix |
Common questions
How do I fix CVE-2026-21513?
Published advisories record a fix for 22 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2026-21513 being actively exploited?
Yes. CVE-2026-21513 is listed in the CISA Known Exploited Vulnerabilities catalog, which means exploitation has been observed in the wild. US federal agencies were required to remediate it by 2026-03-03. Treat it as a priority whatever its CVSS score says.
How severe is CVE-2026-21513?
CVE-2026-21513 has a CVSS v3 base score of 8.8, rated important. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-21513 affect?
Published advisories record a fix for Windows 10 Version 1607 (Windows), Windows 10 Version 1809 (Windows), Windows 10 Version 21H2 (Windows), Windows 10 Version 22H2 (Windows), and 18 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
Embed a live status badge for CVE-2026-21513
Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-03-30.