{
  "id": "CVE-2021-22991",
  "url": "https://spydr.io/cve/CVE-2021-22991",
  "published": "2021-03-31T18:15:14.787Z",
  "modified": "2026-06-17T03:38:10.083Z",
  "score": 9.8,
  "severity": "critical",
  "cvss_version": "3.1",
  "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
  "score_source": "NVD",
  "epss": 0.61064,
  "epss_percentile": 0.99139,
  "exploited": true,
  "kev": {
    "added": "2022-01-18",
    "due": "2022-02-01",
    "action": "Apply updates per vendor instructions.",
    "ransomware": "Unknown",
    "name": "F5 BIG-IP Traffic Management Microkernel Buffer Overflow",
    "notes": "https://nvd.nist.gov/vuln/detail/CVE-2021-22991"
  },
  "ssvc_exploitation": "active",
  "vendors": [
    "f5"
  ],
  "products": [
    "BIG-IP"
  ],
  "cwes": [
    "CWE-119"
  ],
  "description": "On BIG-IP versions 16.0.x before 16.0.1.1, 15.1.x before 15.1.2.1, 14.1.x before 14.1.4, 13.1.x before 13.1.3.6, and 12.1.x before 12.1.5.3, undisclosed requests to a virtual server may be incorrectly handled by the Traffic Management Microkernel (TMM) URI normalization, which may trigger a buffer overflow, resulting in a DoS attack. In certain situations, it may theoretically allow bypass of URL based access control or remote code execution (RCE). Note: Software versions which have reached End of Software Development (EoSD) are not evaluated.",
  "status": "Analyzed",
  "score_type": "Primary",
  "scores": {
    "cvss_v40": null,
    "cvss_v31": 9.8,
    "cvss_v30": null
  },
  "references": [
    {
      "url": "https://support.f5.com/csp/article/K56715231",
      "tags": [
        "Vendor Advisory"
      ]
    },
    {
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-22991",
      "tags": [
        "US Government Resource"
      ]
    }
  ],
  "nvd_url": "https://nvd.nist.gov/vuln/detail/CVE-2021-22991",
  "covered_in": [],
  "attribution": [
    {
      "source": "NVD",
      "url": "https://nvd.nist.gov",
      "notice": "This product uses data from the NVD API but is not endorsed or certified by the NVD."
    },
    {
      "source": "CISA KEV",
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog",
      "notice": "Known exploited vulnerabilities from the CISA KEV catalog."
    },
    {
      "source": "FIRST EPSS",
      "url": "https://www.first.org/epss",
      "notice": "Exploit prediction scores from FIRST EPSS."
    }
  ]
}