{
  "fix": "Mozilla Firefox (en-US) 121.0",
  "url": "https://patchblox.com/security/fix/windows-app/mozilla.firefox-121.0",
  "summary": "Mozilla Firefox (en-US) 121.0, released December 20, 2023, fixes 15 CVEs in Mozilla Firefox (en-US). None of them is reported as exploited. Patch Radar priority: High. The latest Mozilla Firefox (en-US) is 159.0, which also fixes every one of these CVEs.",
  "platform": "windows-app",
  "type": "app-version",
  "title": "Mozilla Firefox (en-US) 121.0",
  "released": "2023-12-20T00:00:00Z",
  "priority": "High",
  "priorityTier": 3,
  "priorityReason": "Closes CVE-2023-6856, high severity",
  "supported": true,
  "cveCount": 15,
  "exploitedCveCount": 0,
  "kevCveCount": 0,
  "ransomwareCveCount": 0,
  "maxEpss": 0.2063,
  "maxCvss": 8.8,
  "appliesTo": [
    {
      "product": "Mozilla Firefox (en-US)",
      "productUrl": "https://patchblox.com/security/product/windows-app/mozilla-firefox-en-us",
      "fixedVersion": "121.0",
      "latestVersion": "159.0",
      "supported": true
    }
  ],
  "supersededBy": {
    "product": "Mozilla Firefox (en-US)",
    "latestVersion": "159.0",
    "productUrl": "https://patchblox.com/security/product/windows-app/mozilla-firefox-en-us"
  },
  "cves": [
    {
      "cveId": "CVE-2023-6856",
      "url": "https://patchblox.com/security/cve/CVE-2023-6856",
      "title": "Mozilla Firefox ESR and 5 others: The WebGL \u0060DrawElementsInstanced\u0060 method was susceptible to a heap buffer overflow when used on systems\u2026",
      "priority": "High",
      "severity": "high",
      "cvss": 8.8,
      "epss": 0.2063,
      "kev": false,
      "ransomware": false,
      "exploited": false,
      "disclosed": false
    },
    {
      "cveId": "CVE-2023-6858",
      "url": "https://patchblox.com/security/cve/CVE-2023-6858",
      "title": "Mozilla Firefox ESR and 5 others: Out-of-bounds Write",
      "priority": "High",
      "severity": "high",
      "cvss": 8.8,
      "epss": 0.01544,
      "kev": false,
      "ransomware": false,
      "exploited": false,
      "disclosed": false
    },
    {
      "cveId": "CVE-2023-6861",
      "url": "https://patchblox.com/security/cve/CVE-2023-6861",
      "title": "Mozilla Firefox ESR and 5 others: The \u0060nsWindow::PickerOpen(void)\u0060 method was susceptible to a heap buffer overflow when running in headless\u2026",
      "priority": "High",
      "severity": "high",
      "cvss": 8.8,
      "epss": 0.01411,
      "kev": false,
      "ransomware": false,
      "exploited": false,
      "disclosed": false
    },
    {
      "cveId": "CVE-2023-6864",
      "url": "https://patchblox.com/security/cve/CVE-2023-6864",
      "title": "Mozilla Firefox ESR and 5 others: Memory safety bugs present in Firefox 120, Firefox ESR 115.5, and Thunderbird 115.5.",
      "priority": "High",
      "severity": "high",
      "cvss": 8.8,
      "epss": 0.01194,
      "kev": false,
      "ransomware": false,
      "exploited": false,
      "disclosed": false
    },
    {
      "cveId": "CVE-2023-6859",
      "url": "https://patchblox.com/security/cve/CVE-2023-6859",
      "title": "Mozilla Firefox ESR and 5 others: A use-after-free condition affected TLS socket creation when under memory pressure.",
      "priority": "High",
      "severity": "high",
      "cvss": 8.8,
      "epss": 0.01092,
      "kev": false,
      "ransomware": false,
      "exploited": false,
      "disclosed": false
    },
    {
      "cveId": "CVE-2023-6863",
      "url": "https://patchblox.com/security/cve/CVE-2023-6863",
      "title": "Mozilla Firefox ESR and 5 others: The \u0060ShutdownObserver()\u0060 was susceptible to potentially undefined behavior due to its reliance on a dynamic\u2026",
      "priority": "High",
      "severity": "high",
      "cvss": 8.8,
      "epss": 0.01037,
      "kev": false,
      "ransomware": false,
      "exploited": false,
      "disclosed": false
    },
    {
      "cveId": "CVE-2023-6865",
      "url": "https://patchblox.com/security/cve/CVE-2023-6865",
      "title": "Mozilla Firefox ESR and 3 others: \u0060EncryptingOutputStream\u0060 was susceptible to exposing uninitialized data.",
      "priority": "High",
      "severity": "medium",
      "cvss": 7.5,
      "epss": 0.00888,
      "kev": false,
      "ransomware": false,
      "exploited": false,
      "disclosed": false
    },
    {
      "cveId": "CVE-2023-6873",
      "url": "https://patchblox.com/security/cve/CVE-2023-6873",
      "title": "Mozilla Firefox ESR and 3 others: Memory safety bugs present in Firefox 120.",
      "priority": "High",
      "severity": "high",
      "cvss": 8.8,
      "epss": 0.00853,
      "kev": false,
      "ransomware": false,
      "exploited": false,
      "disclosed": false
    },
    {
      "cveId": "CVE-2023-6866",
      "url": "https://patchblox.com/security/cve/CVE-2023-6866",
      "title": "Mozilla Firefox ESR and 3 others: TypedArrays can be fallible and lacked proper exception handling.",
      "priority": "High",
      "severity": "Medium",
      "cvss": 8.8,
      "epss": 0.00681,
      "kev": false,
      "ransomware": false,
      "exploited": false,
      "disclosed": false
    },
    {
      "cveId": "CVE-2023-6860",
      "url": "https://patchblox.com/security/cve/CVE-2023-6860",
      "title": "Mozilla Firefox ESR and 5 others: The \u0060VideoBridge\u0060 allowed any content process to use textures produced by remote decoders.",
      "priority": "Routine",
      "severity": "medium",
      "cvss": 6.5,
      "epss": 0.00958,
      "kev": false,
      "ransomware": false,
      "exploited": false,
      "disclosed": false
    },
    {
      "cveId": "CVE-2023-6135",
      "url": "https://patchblox.com/security/cve/CVE-2023-6135",
      "title": "Mozilla Firefox ESR and 3 others: Multiple NSS NIST curves were susceptible to a side-channel attack known as \u0022Minerva\u0022.",
      "priority": "Routine",
      "severity": "Moderate",
      "cvss": 4.3,
      "epss": 0.00714,
      "kev": false,
      "ransomware": false,
      "exploited": false,
      "disclosed": false
    },
    {
      "cveId": "CVE-2023-6867",
      "url": "https://patchblox.com/security/cve/CVE-2023-6867",
      "title": "Mozilla Firefox ESR and 3 others: The timing of a button click causing a popup to disappear was approximately the same length as the anti-clickjacking\u2026",
      "priority": "Routine",
      "severity": "medium",
      "cvss": 6.1,
      "epss": 0.00683,
      "kev": false,
      "ransomware": false,
      "exploited": false,
      "disclosed": false
    },
    {
      "cveId": "CVE-2023-6872",
      "url": "https://patchblox.com/security/cve/CVE-2023-6872",
      "title": "Mozilla Firefox ESR and 3 others: Browser tab titles were being leaked by GNOME to system logs.",
      "priority": "Routine",
      "severity": "Medium",
      "cvss": 6.5,
      "epss": 0.00646,
      "kev": false,
      "ransomware": false,
      "exploited": false,
      "disclosed": false
    },
    {
      "cveId": "CVE-2023-6869",
      "url": "https://patchblox.com/security/cve/CVE-2023-6869",
      "title": "Mozilla Firefox ESR and 3 others: A \u0060\u0026lt;dialog\u003E\u0060 element could have been manipulated to paint content outside of a sandboxed iframe.",
      "priority": "Routine",
      "severity": "Medium",
      "cvss": 6.5,
      "epss": 0.00559,
      "kev": false,
      "ransomware": false,
      "exploited": false,
      "disclosed": false
    },
    {
      "cveId": "CVE-2023-6871",
      "url": "https://patchblox.com/security/cve/CVE-2023-6871",
      "title": "Mozilla Firefox ESR and 3 others: Under certain conditions, Firefox did not display a warning when a user attempted to navigate to a new\u2026",
      "priority": "Routine",
      "severity": "Medium",
      "cvss": 4.3,
      "epss": 0.00493,
      "kev": false,
      "ransomware": false,
      "exploited": false,
      "disclosed": false
    }
  ],
  "dataAsOf": "2026-11-09T01:18:40Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}