CISA KEV · Known exploitedHigh

CVE-2026-21513

Microsoft Windows

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

CVSS: 8.8
EPSS: 15.4%
CISA KEV: Listed
Published: 2026.02.11

PRIORITY ASSESSMENT

Immediate review

CISA has listed this vulnerability in the Known Exploited Vulnerabilities catalog.

Known exploitationConfirmed by CISA KEV

Exploit probability15.4%

Technical severityCVSS 8.8

Vulnerability overview

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

Affected product and versions

Product: Microsoft Windows
Affected versions: 10.0.14393.0, 10.0.17763.0, 10.0.19044.0, 10.0.19045.0, 10.0.22631.0, 10.0.26100.0, 10.0.26200.0, 10.0.28000.0, 6.2.9200.0, 6.3.9600.0, 10.0.20348.0, 10.0.25398.0, < 10.0.14393.8868, < 10.0.17763.8389, < 10.0.19044.6937, < 10.0.19045.6937, < 10.0.22631.6649, < 10.0.26100.7781, < 10.0.26200.7781, r2
Fixed versions: 10.0.14393.8868, 10.0.17763.8389, 10.0.19044.6937, 10.0.19045.6937, 10.0.22631.6649, 10.0.26100.7781, 10.0.26200.7781, 10.0.20348.4711, 10.0.25398.2149, 10.0.26100.32313

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

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.

Due date: 2026.03.03

1
Identify
Confirm that Microsoft Windows and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CWE: CWE-693
KEV added: 2026.02.10
Ransomware use: 미확인