Security Digest · Vulnerability record · Known exploited
CVE-2026-21513: Microsoft MSHTML Framework Protection Mechanism Failure Vulnerability
Exploited in the wild (CISA KEV). Protection mechanism failure in MSHTML Framework allows an unauthorized attacker to bypass a security feature over a network.
CISA KEV · added 2026-02-10 CVSS 8.8 High EPSS 15.9% · p97
Should you act?
Exploited: patch now if you run it
CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Yes, if you run Microsoft Windows. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-02-10, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-03-03; treat that as the outer limit, not the target.
- EPSS 15.9%, percentile 97: FIRST’s model estimates a 15.9% chance of exploitation activity in the next 30 days, higher than 97% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Needs a user to click or open something. Phishing makes that realistic, but it is not wormable.
What it is
Protection mechanism failure in MSHTML Framework allows an unauthorized attacker to bypass a security feature over a network.
CISA’s summary
Microsoft MSHTML Framework contains a protection mechanism failure vulnerability that could allow an unauthorized attacker to bypass a security feature over a network.
Weakness type: CWE-693.
Product: Microsoft Windows · Assigned by: microsoft · Published: 2026-02-10
Affected and fixed versions
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| Microsoft | Windows 10 Version 1607 | 10.0.14393.0 < 10.0.14393.8868 |
| Microsoft | Windows 10 Version 1809 | 10.0.17763.0 < 10.0.17763.8389 |
| Microsoft | Windows 10 Version 21H2 | 10.0.19044.0 < 10.0.19044.6937 |
| Microsoft | Windows 10 Version 22H2 | 10.0.19045.0 < 10.0.19045.6937 |
| Microsoft | Windows 11 version 22H3 | 10.0.22631.0 < 10.0.22631.6649 |
| Microsoft | Windows 11 Version 23H2 | 10.0.22631.0 < 10.0.22631.6649 |
| Microsoft | Windows 11 Version 24H2 | 10.0.26100.0 < 10.0.26100.7840 |
| Microsoft | Windows 11 Version 25H2 | 10.0.26200.0 < 10.0.26200.7840 |
| Microsoft | Windows 11 version 26H1 | 10.0.28000.0 < 10.0.28000.1575 |
| Microsoft | Windows 11 Version 26H1 | 10.0.28000.0 < 10.0.28000.1575 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| microsoft | 3.1 | 8.8 High | 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 (remotely reachable)
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: required (a user must click/open something)
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: added 2026-02-10; federal due date 2026-03-03. Known ransomware use: Unknown.
- CISA 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.
- CISA SSVC assessment: exploitation active, automatable no, technical impact total.
- FIRST EPSS (model of 2026-10-21): 15.85% probability of exploitation activity in the next 30 days; percentile 97.
Timeline
- — Added to CISA’s Known Exploited Vulnerabilities catalog
- — CVE record published by microsoft
- — CISA remediation deadline for US federal agencies
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vendor and project advisories, patches
- MSHTML Framework Security Feature Bypass Vulnerability msrc.microsoft.com
- Listed in CISA KEV notes (msrc.microsoft.com) msrc.microsoft.com
Vulnerability records
- CVE.org record CVE-2026-21513 cve.org
- NVD entry CVE-2026-21513 nvd.nist.gov
Government
Other references from the CVE record and advisory
- vicarius.io vicarius.io
- vicarius.io vicarius.io
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