CVE-2026-21513: Microsoft MSHTML Framework protection mechanism failure

CVE-2026-21513 · Severity: critical · CVSS 8.8 · Exploited in the wild · Published 2026-02-10

A security flaw has been identified in the Microsoft MSHTML Framework, a core component used by Windows to render web content and documents. This vulnerability allows an attacker to bypass built-in security protections, potentially leading to unauthorized access or the execution of malicious code if a user visits a compromised website or opens a malicious file. This issue is actively being exploited in the wild, posing a significant risk to corporate data and system integrity.

Technologies: Microsoft Windows. Vendors: Microsoft.

Quick answers

Is CVE-2026-21513 exploited in the wild?
Yes. CVE-2026-21513 is known to be exploited in the wild, first recorded on 10 February 2026. Treat it as urgent.
How severe is CVE-2026-21513?
Critical severity, with a CVSS score of 8.8, published 10 February 2026.
Which products and versions are affected?
Microsoft Windows 10 up to (excluding) 10.0.14393.8868, 10.0.17763.8389, 10.0.19045.6937, 10.0.19044.6937; Microsoft Windows 11 up to (excluding) 10.0.26100.7781, 10.0.22631.6649, 10.0.26200.7781; Microsoft Windows Server 2012 R2 and base versions; Microsoft Windows Server 2016 up to (excluding) 10.0.14393.8868; and 2 more.
Is there a fix for CVE-2026-21513?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-21513 attacked?
It is attacked over the network, in an operating system.
Am I affected by CVE-2026-21513?
Check whether you run Microsoft Windows. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A protection mechanism failure (CWE-693) exists in the Microsoft MSHTML Framework. The vulnerability allows a remote, unauthenticated attacker to bypass security features by convincing a user to interact with malicious content, such as a specially crafted website or document. The attack vector is network-based with low complexity, though it requires user interaction (UI:R). Successful exploitation can result in high impacts on confidentiality, integrity, and availability. This vulnerability is confirmed to be exploited in the wild and is tracked in the CISA Known Exploited Vulnerabilities (KEV) catalog. Microsoft has released updates to address this issue across various versions of Windows and Windows Server.

Affected products

  • Microsoft Windows 10 up to (excluding) 10.0.14393.8868, 10.0.17763.8389, 10.0.19045.6937, 10.0.19044.6937
  • Microsoft Windows 11 up to (excluding) 10.0.26100.7781, 10.0.22631.6649, 10.0.26200.7781
  • Microsoft Windows Server 2012 R2 and base versions
  • Microsoft Windows Server 2016 up to (excluding) 10.0.14393.8868
  • Microsoft Windows Server 2019
  • Microsoft MSHTML Framework

Timeline

  • 2026-02-10: disclosed
  • 2026-02-10: advisory
  • 2026-02-10: kev added: Added to CISA KEV catalog due to active exploitation.
  • 2026-02-10: exploited

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