{
  "cveId": "CVE-2021-23997",
  "url": "https://patchblox.com/security/cve/CVE-2021-23997",
  "summary": "CVE-2021-23997 is fixed in 4 products on 2 platforms, first by firefox 88.0\u002Bbuild2-0ubuntu0.18.04.2, released April 25, 2021. It is not reported as exploited. Patch Radar priority: High.",
  "title": "Firefox ESR and 1 other: Due to unexpected data type conversions, a use-after-free could have occurred when interacting with the\u2026",
  "description": "Due to unexpected data type conversions, a use-after-free could have occurred when interacting with the font cache. We presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability affects Firefox \u003C 88.",
  "published": "2021-04-18T17:00:00Z",
  "severity": "Medium",
  "cvss": 8.8,
  "epss": 0.00816,
  "epssPercentile": 0.57348,
  "priority": "High",
  "priorityTier": 3,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://nvd.nist.gov/vuln/detail/CVE-2021-23997",
  "fixes": [
    {
      "platform": "windows-app",
      "product": "Mozilla Firefox ESR (en-US)",
      "fixedVersion": "91.0",
      "fix": "Mozilla Firefox ESR (en-US) 91.0",
      "url": "https://patchblox.com/security/fix/windows-app/mozilla.firefox.esr-91.0",
      "released": "2021-08-04T00:00:00Z"
    },
    {
      "platform": "linux",
      "product": "firefox",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "88.0\u002Bbuild2-0ubuntu0.18.04.2",
      "fix": "firefox 88.0\u002Bbuild2-0ubuntu0.18.04.2",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-firefox-88.0-build2-0ubuntu0.18.04.2",
      "released": "2021-04-25T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "firefox",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "88.0\u002Bbuild2-0ubuntu0.20.04.1",
      "fix": "firefox 88.0\u002Bbuild2-0ubuntu0.20.04.1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-firefox-88.0-build2-0ubuntu0.20.04.1",
      "released": "2021-04-25T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "firefox-geckodriver",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "88.0\u002Bbuild2-0ubuntu0.18.04.2",
      "fix": "firefox-geckodriver 88.0\u002Bbuild2-0ubuntu0.18.04.2",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-firefox-geckodriver-88.0-build2-0ubuntu0.18.04.2",
      "released": "2021-04-25T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "firefox-geckodriver",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "88.0\u002Bbuild2-0ubuntu0.20.04.1",
      "fix": "firefox-geckodriver 88.0\u002Bbuild2-0ubuntu0.20.04.1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-firefox-geckodriver-88.0-build2-0ubuntu0.20.04.1",
      "released": "2021-04-25T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "firefox-mozsymbols",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "88.0\u002Bbuild2-0ubuntu0.18.04.2",
      "fix": "firefox-mozsymbols 88.0\u002Bbuild2-0ubuntu0.18.04.2",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-firefox-mozsymbols-88.0-build2-0ubuntu0.18.04.2",
      "released": "2021-04-25T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "firefox-mozsymbols",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "88.0\u002Bbuild2-0ubuntu0.20.04.1",
      "fix": "firefox-mozsymbols 88.0\u002Bbuild2-0ubuntu0.20.04.1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-firefox-mozsymbols-88.0-build2-0ubuntu0.20.04.1",
      "released": "2021-04-25T17:00:00Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T19:12:23Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}