CVE-2026-21513: listed in the CISA KEV catalog

CVE-2026-21513 · CVSS 8.8 HIGH · EPSS 16% · KEV 2026-02-10 · patch available

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

Is CVE-2026-21513 exploited?

• Listed in the CISA KEV catalog on 2026-02-10.
• Federal remediation due 2026-03-03.
• Past that date by 211 days.
• EPSS puts exploitation in the next 30 days at 16%.
• Public exploit code: none found in monitored sources.

Which products and versions are affected?

• 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 Server 2012 · >= 6.2.9200.0, < 6.2.9200.25923
• Microsoft · Windows Server 2012 (Server Core installation) · >= 6.2.9200.0, < 6.2.9200.25923
• Microsoft · Windows Server 2012 R2 · >= 6.3.9600.0, < 6.3.9600.23022
• Microsoft · Windows Server 2012 R2 (Server Core installation) · >= 6.3.9600.0, < 6.3.9600.23022
• Microsoft · Windows Server 2016 · >= 10.0.14393.0, < 10.0.14393.8868
• Microsoft · Windows Server 2016 (Server Core installation) · >= 10.0.14393.0, < 10.0.14393.8868
• Microsoft · Windows Server 2019 · >= 10.0.17763.0, < 10.0.17763.8389
• Microsoft · Windows Server 2019 (Server Core installation) · >= 10.0.17763.0, < 10.0.17763.8389
• Microsoft · Windows Server 2022 · >= 10.0.20348.0, < 10.0.20348.4773
• Microsoft · Windows Server 2022, 23H2 Edition (Server Core installation) · >= 10.0.25398.0, < 10.0.25398.2149
• Microsoft · Windows 11 Version 26H1 for ARM64-based Systems · < 10.0.28000.1575
• Microsoft · Windows 11 version 26H1 for x64-based Systems · < 10.0.28000.1575
• Microsoft · Windows 10 Version 1809 for 32-bit Systems · < 10.0.17763.8389
• Microsoft · Windows 10 Version 1809 for x64-based Systems · < 10.0.17763.8389
• Microsoft · Windows Server 2022 (Server Core installation) · < 10.0.20348.4773, < 10.0.20348.4711
• Microsoft · Windows 10 Version 21H2 for 32-bit Systems · < 10.0.19044.6937
• Microsoft · Windows 10 Version 21H2 for ARM64-based Systems · < 10.0.19044.6937
• Microsoft · Windows 10 Version 21H2 for x64-based Systems · < 10.0.19044.6937
• Microsoft · Windows Server 2025 · < 10.0.26100.32370, < 10.0.26100.32313
• Microsoft · Windows Server 2025 (Server Core installation) · < 10.0.26100.32370, < 10.0.26100.32313
• Microsoft · Windows 11 Version 25H2 for ARM64-based Systems · < 10.0.26200.7840, < 10.0.26200.7781
• Microsoft · Windows 11 Version 25H2 for x64-based Systems · < 10.0.26200.7840, < 10.0.26200.7781
• Microsoft · Windows 11 Version 23H2 for ARM64-based Systems · < 10.0.22631.6649
• Microsoft · Windows 11 Version 23H2 for x64-based Systems · < 10.0.22631.6649

Is there a patch?

• KB5077179
• KB5075904
• KB5075906
• KB5075943
• KB5075912
• KB5075899
• KB5075942
• KB5077181
• KB5077212
• KB5075941

What PlainSec published about CVE-2026-21513

• APT28 Expands Supply-Chain Attacks Using Fresh Office Zero-Days (2026-04-09)
• APT28 Tied to CVE-2026-21513 MSHTML 0-Day Exploited Before Feb 2026 Patch Tuesday (2026-03-03)

Primary sources

• NVD record
• CISA KEV catalog
• Microsoft KB5077179
• Microsoft KB5075904
• Microsoft KB5075906
• Microsoft KB5075943
• Microsoft KB5075912
• Microsoft KB5075899
• Microsoft KB5075942
• Microsoft KB5077181

KEV and EPSS are re-checked daily. Record last updated 2026-09-09.