CVE-2026-21513
Actively exploited. CVE-2026-21513 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-02-10) — exploitation has been observed in the wild, and US federal agencies are required to remediate it under BOD 22-01. Treat patching as urgent.
Microsoft MSHTML Framework contains a protection mechanism failure vulnerability that could allow an unauthorized attacker to bypass a security feature over a network.
CSIRTS triage
- What
- A protection mechanism failure vulnerability could allow an unauthorized attacker to bypass a security feature over a network.
- Who is affected
- Deployments of Microsoft MSHTML Framework.
- Urgency
- Remediation is urgent due to active exploitation and critical severity.
- Action
- Apply the latest security patch provided by Microsoft.
AI-assisted analysis generated from the source advisory — verify against the original.
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Exploitation outlook
- Exploitation confirmedAlready exploited in the wild (CISA KEV) — the prediction phase is over. Patch now. Riskier than 96% of all EPSS-scored CVEs.
Advisory coverage (1)
- criticalexploitedCVE-2026-21513: Microsoft MSHTML Framework Protection Mechanism Failure Vulnerabilitycisa-kev · 2026-02-10
External references
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[](https://www.csirts.com/cve/CVE-2026-21513)