{
  "crds_version": "0.1",
  "kind": "base",
  "id": "crds:cve-2026-21513",
  "revision": 1,
  "title": "Windows MSHTML — safeguard failure over the network",
  "summary": "A safeguard in Windows' legacy web rendering framework (MSHTML) does not hold, letting an attacker on the network get past a security feature. Microsoft's entry does not say which feature that is.",
  "source_type": "cve",
  "severity": "high",
  "cvss": {
    "score": 8.8,
    "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
    "version": "3.1"
  },
  "epss": 0.15642,
  "exploitation": {
    "known_exploited": true,
    "exploit_available": false,
    "attack_complexity": "low",
    "kev_added": "2026-02-10",
    "prerequisites": "A network position from which to deliver the crafted content."
  },
  "kill_chain": "defense_evasion",
  "recommended_action": "Install the Microsoft update for this CVE now; the legacy rendering engine is reached through more than the browser, so patch servers and workstations alike.",
  "confidence": "medium",
  "provenance": [
    {
      "fields": [
        "cvss",
        "exploitation.attack_complexity",
        "exploitation.exploit_available",
        "references",
        "published_at"
      ],
      "source": "https://nvd.nist.gov/vuln/detail/CVE-2026-21513",
      "retrieved_at": "2026-09-24T08:51:39.744Z",
      "confidence": "high",
      "extractor": "scrty-crds-pipeline/0.1"
    },
    {
      "fields": [
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        "exploitation.kev_added"
      ],
      "source": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog",
      "retrieved_at": "2026-09-24T08:51:39.744Z",
      "confidence": "high",
      "extractor": "scrty-crds-pipeline/0.1"
    },
    {
      "fields": [
        "epss"
      ],
      "source": "https://api.first.org/data/v1/epss?cve=CVE-2026-21513",
      "retrieved_at": "2026-09-24T08:51:39.744Z",
      "confidence": "high",
      "extractor": "scrty-crds-pipeline/0.1"
    },
    {
      "fields": [
        "title",
        "summary",
        "severity",
        "remediation",
        "mitre_attack",
        "kill_chain",
        "recommended_action",
        "confidence",
        "tags",
        "exploitation.prerequisites"
      ],
      "source": "https://nvd.nist.gov/vuln/detail/CVE-2026-21513",
      "retrieved_at": "2026-09-24T08:51:39.744Z",
      "confidence": "high",
      "extractor": "claude-code"
    }
  ],
  "references": [
    {
      "type": "cve",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-21513",
      "label": "NVD record"
    },
    {
      "type": "cisa",
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog",
      "label": "CISA Known Exploited Vulnerabilities catalog"
    },
    {
      "type": "vendor_advisory",
      "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21513"
    },
    {
      "type": "vendor_advisory",
      "url": "https://www.vicarius.io/vsociety/posts/cve-2026-21513-mitigation-script-security-feature-bypass-vulnerability-in-mshtml-framework"
    },
    {
      "type": "writeup",
      "url": "https://www.vicarius.io/vsociety/posts/cve-2026-21513-detection-script-security-feature-bypass-vulnerability-in-mshtml-framework"
    }
  ],
  "published_at": "2026-02-10T18:16:33.643Z",
  "issued_at": "2026-09-24T08:51:39.744Z",
  "tags": [
    "microsoft",
    "windows",
    "mshtml",
    "security-feature-bypass",
    "kev"
  ]
}