{
  "cveId": "CVE-2020-6820",
  "url": "https://patchblox.com/security/cve/CVE-2020-6820",
  "summary": "CVE-2020-6820 is fixed in 10 products on 2 platforms, first by firefox 74.0.1\u002Bbuild1-0ubuntu0.18.04.1, released April 2, 2020. It is being exploited: CISA added it to the Known Exploited Vulnerabilities catalog on November 3, 2021. Patch Radar priority: Patch now.",
  "title": "Mozilla Firefox And Thunderbird Use-After-Free Vulnerability",
  "description": "Under certain conditions, when handling a ReadableStream, a race condition can cause a use-after-free. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability affects Thunderbird \u003C 68.7.0, Firefox \u003C 74.0.1, and Firefox ESR \u003C 68.6.1.",
  "published": "2020-04-02T17:00:00Z",
  "severity": "Critical",
  "cvss": 8.8,
  "cwe": "CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization (\u0027Race Condition\u0027)",
  "epss": 0.07063,
  "epssPercentile": 0.94244,
  "priority": "Patch now",
  "priorityTier": 1,
  "exploited": true,
  "vendorExploited": true,
  "disclosed": false,
  "kev": {
    "added": "2021-11-03T00:00:00Z",
    "due": "2022-05-03T00:00:00Z",
    "ransomware": false,
    "requiredAction": "Apply updates per vendor instructions."
  },
  "vendorAdvisory": "https://nvd.nist.gov/vuln/detail/CVE-2020-6820",
  "fixes": [
    {
      "platform": "windows-app",
      "product": "Mozilla Firefox ESR (en-US)",
      "fixedVersion": "78.0esr",
      "fix": "Mozilla Firefox ESR (en-US) 78.0esr",
      "url": "https://patchblox.com/security/fix/windows-app/mozilla.firefox.esr-78.0esr",
      "released": "2020-06-25T00:00:00Z"
    },
    {
      "platform": "linux",
      "product": "firefox",
      "release": "RHEL 8",
      "fixedVersion": "0:68.6.1-1.el8_1",
      "fix": "RHSA-2020:1341",
      "url": "https://patchblox.com/security/fix/linux/rhsa-2020-1341",
      "released": "2020-04-07T00:00:00Z"
    },
    {
      "platform": "linux",
      "product": "firefox",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "74.0.1\u002Bbuild1-0ubuntu0.18.04.1",
      "fix": "firefox 74.0.1\u002Bbuild1-0ubuntu0.18.04.1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-firefox-74.0.1-build1-0ubuntu0.18.04.1",
      "released": "2020-04-02T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "firefox",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "75.0\u002Bbuild3-0ubuntu1",
      "fix": "firefox 75.0\u002Bbuild3-0ubuntu1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-firefox-75.0-build3-0ubuntu1",
      "released": "2020-04-06T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "firefox",
      "release": "ol 8",
      "fixedVersion": "0:68.6.1-1.0.1.el8_1",
      "fix": "ELSA-2020-1341",
      "url": "https://patchblox.com/security/fix/linux/elsa-2020-1341",
      "released": "2020-04-09T00:00:00Z"
    },
    {
      "platform": "linux",
      "product": "firefox-geckodriver",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "74.0.1\u002Bbuild1-0ubuntu0.18.04.1",
      "fix": "firefox-geckodriver 74.0.1\u002Bbuild1-0ubuntu0.18.04.1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-firefox-geckodriver-74.0.1-build1-0ubuntu0.18.04.1",
      "released": "2020-04-02T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "firefox-geckodriver",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "75.0\u002Bbuild3-0ubuntu1",
      "fix": "firefox-geckodriver 75.0\u002Bbuild3-0ubuntu1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-firefox-geckodriver-75.0-build3-0ubuntu1",
      "released": "2020-04-06T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "firefox-mozsymbols",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "74.0.1\u002Bbuild1-0ubuntu0.18.04.1",
      "fix": "firefox-mozsymbols 74.0.1\u002Bbuild1-0ubuntu0.18.04.1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-firefox-mozsymbols-74.0.1-build1-0ubuntu0.18.04.1",
      "released": "2020-04-02T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "firefox-mozsymbols",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "75.0\u002Bbuild3-0ubuntu1",
      "fix": "firefox-mozsymbols 75.0\u002Bbuild3-0ubuntu1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-firefox-mozsymbols-75.0-build3-0ubuntu1",
      "released": "2020-04-06T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "thunderbird",
      "release": "RHEL 8",
      "fixedVersion": "0:68.7.0-1.el8_1",
      "fix": "RHSA-2020:1495",
      "url": "https://patchblox.com/security/fix/linux/rhsa-2020-1495",
      "released": "2020-04-16T00:00:00Z"
    },
    {
      "platform": "linux",
      "product": "thunderbird",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "1:68.7.0\u002Bbuild1-0ubuntu0.18.04.1",
      "fix": "thunderbird 1:68.7.0\u002Bbuild1-0ubuntu0.18.04.1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-thunderbird-1-68.7.0-build1-0ubuntu0.18.04.1",
      "released": "2020-04-06T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "thunderbird",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "1:68.7.0\u002Bbuild1-0ubuntu1",
      "fix": "thunderbird 1:68.7.0\u002Bbuild1-0ubuntu1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-thunderbird-1-68.7.0-build1-0ubuntu1",
      "released": "2020-04-06T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "thunderbird",
      "release": "ol 8",
      "fixedVersion": "0:68.7.0-1.0.1.el8_1",
      "fix": "ELSA-2020-1495",
      "url": "https://patchblox.com/security/fix/linux/elsa-2020-1495",
      "released": "2020-04-18T00:00:00Z"
    },
    {
      "platform": "linux",
      "product": "thunderbird-gnome-support",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "1:68.7.0\u002Bbuild1-0ubuntu0.18.04.1",
      "fix": "thunderbird-gnome-support 1:68.7.0\u002Bbuild1-0ubuntu0.18.04.1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-thunderbird-gnome-support-1-68.7.0-build1-0ubuntu0.18.04.1",
      "released": "2020-04-06T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "thunderbird-gnome-support",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "1:68.7.0\u002Bbuild1-0ubuntu1",
      "fix": "thunderbird-gnome-support 1:68.7.0\u002Bbuild1-0ubuntu1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-thunderbird-gnome-support-1-68.7.0-build1-0ubuntu1",
      "released": "2020-04-06T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "thunderbird-mozsymbols",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "1:68.7.0\u002Bbuild1-0ubuntu0.18.04.1",
      "fix": "thunderbird-mozsymbols 1:68.7.0\u002Bbuild1-0ubuntu0.18.04.1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-thunderbird-mozsymbols-1-68.7.0-build1-0ubuntu0.18.04.1",
      "released": "2020-04-06T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "thunderbird-mozsymbols",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "1:68.7.0\u002Bbuild1-0ubuntu1",
      "fix": "thunderbird-mozsymbols 1:68.7.0\u002Bbuild1-0ubuntu1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-thunderbird-mozsymbols-1-68.7.0-build1-0ubuntu1",
      "released": "2020-04-06T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "xul-ext-calendar-timezones",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "1:68.7.0\u002Bbuild1-0ubuntu0.18.04.1",
      "fix": "xul-ext-calendar-timezones 1:68.7.0\u002Bbuild1-0ubuntu0.18.04.1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-xul-ext-calendar-timezones-1-68.7.0-build1-0ubuntu0.18.04.1",
      "released": "2020-04-06T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "xul-ext-calendar-timezones",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "1:68.7.0\u002Bbuild1-0ubuntu1",
      "fix": "xul-ext-calendar-timezones 1:68.7.0\u002Bbuild1-0ubuntu1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-xul-ext-calendar-timezones-1-68.7.0-build1-0ubuntu1",
      "released": "2020-04-06T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "xul-ext-gdata-provider",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "1:68.7.0\u002Bbuild1-0ubuntu0.18.04.1",
      "fix": "xul-ext-gdata-provider 1:68.7.0\u002Bbuild1-0ubuntu0.18.04.1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-xul-ext-gdata-provider-1-68.7.0-build1-0ubuntu0.18.04.1",
      "released": "2020-04-06T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "xul-ext-gdata-provider",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "1:68.7.0\u002Bbuild1-0ubuntu1",
      "fix": "xul-ext-gdata-provider 1:68.7.0\u002Bbuild1-0ubuntu1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-xul-ext-gdata-provider-1-68.7.0-build1-0ubuntu1",
      "released": "2020-04-06T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "xul-ext-lightning",
      "release": "Ubuntu 18.04.6 LTS (bionic)",
      "fixedVersion": "1:68.7.0\u002Bbuild1-0ubuntu0.18.04.1",
      "fix": "xul-ext-lightning 1:68.7.0\u002Bbuild1-0ubuntu0.18.04.1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-bionic-xul-ext-lightning-1-68.7.0-build1-0ubuntu0.18.04.1",
      "released": "2020-04-06T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "xul-ext-lightning",
      "release": "Ubuntu 20.04 LTS (focal)",
      "fixedVersion": "1:68.7.0\u002Bbuild1-0ubuntu1",
      "fix": "xul-ext-lightning 1:68.7.0\u002Bbuild1-0ubuntu1",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-focal-xul-ext-lightning-1-68.7.0-build1-0ubuntu1",
      "released": "2020-04-06T17:00:00Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T00:53:09Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}