# CVE-2020-12426: Firefox ESR: Mozilla developers and community members reported memory safety bugs present in Firefox 77. CVE-2020-12426 is fixed in 10 products on 2 platforms, first by Mozilla Firefox ESR (en-US) 78.0esr, released June 25, 2020. It is not reported as exploited. Patch Radar priority: High. - Web page: https://patchblox.com/security/cve/CVE-2020-12426 - Priority: High - CVSS: 8.8 (Medium) - EPSS: 0.0161 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Jun 30, 2020 - Vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2020-12426 ## Description Mozilla developers and community members reported memory safety bugs present in Firefox 77. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 78. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Windows apps | Mozilla Firefox ESR (en-US) | 78.0esr | [Mozilla Firefox ESR (en-US) 78.0esr](https://patchblox.com/security/data/fix/windows-app/mozilla.firefox.esr-78.0esr.md) | Jun 25, 2020 | | Linux | firefox Ubuntu 18.04.6 LTS (bionic) | 78.0.1+build1-0ubuntu0.18.04.1 | [firefox 78.0.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-78.0.1-build1-0ubuntu0.18.04.1.md) | Jun 30, 2020 | | Linux | firefox Ubuntu 20.04 LTS (focal) | 78.0.1+build1-0ubuntu0.20.04.1 | [firefox 78.0.1+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-78.0.1-build1-0ubuntu0.20.04.1.md) | Jun 30, 2020 | | Linux | firefox-geckodriver Ubuntu 18.04.6 LTS (bionic) | 78.0.1+build1-0ubuntu0.18.04.1 | [firefox-geckodriver 78.0.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-geckodriver-78.0.1-build1-0ubuntu0.18.04.1.md) | Jun 30, 2020 | | Linux | firefox-geckodriver Ubuntu 20.04 LTS (focal) | 78.0.1+build1-0ubuntu0.20.04.1 | [firefox-geckodriver 78.0.1+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-geckodriver-78.0.1-build1-0ubuntu0.20.04.1.md) | Jun 30, 2020 | | Linux | firefox-mozsymbols Ubuntu 18.04.6 LTS (bionic) | 78.0.1+build1-0ubuntu0.18.04.1 | [firefox-mozsymbols 78.0.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-mozsymbols-78.0.1-build1-0ubuntu0.18.04.1.md) | Jun 30, 2020 | | Linux | firefox-mozsymbols Ubuntu 20.04 LTS (focal) | 78.0.1+build1-0ubuntu0.20.04.1 | [firefox-mozsymbols 78.0.1+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-mozsymbols-78.0.1-build1-0ubuntu0.20.04.1.md) | Jun 30, 2020 | | Linux | thunderbird Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | [thunderbird 1:78.8.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-thunderbird-1-78.8.1-build1-0ubuntu0.18.04.1.md) | Apr 22, 2021 | | Linux | thunderbird Ubuntu 20.04 LTS (focal) | 1:78.7.1+build1-0ubuntu0.20.04.1 | [thunderbird 1:78.7.1+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-thunderbird-1-78.7.1-build1-0ubuntu0.20.04.1.md) | Jan 25, 2021 | | Linux | thunderbird-gnome-support Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | [thunderbird-gnome-support 1:78.8.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-thunderbird-gnome-support-1-78.8.1-build1-0ubuntu0.18.04.1.md) | Apr 22, 2021 | | Linux | thunderbird-gnome-support Ubuntu 20.04 LTS (focal) | 1:78.7.1+build1-0ubuntu0.20.04.1 | [thunderbird-gnome-support 1:78.7.1+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-thunderbird-gnome-support-1-78.7.1-build1-0ubuntu0.20.04.1.md) | Jan 25, 2021 | | Linux | thunderbird-mozsymbols Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | [thunderbird-mozsymbols 1:78.8.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-thunderbird-mozsymbols-1-78.8.1-build1-0ubuntu0.18.04.1.md) | Apr 22, 2021 | | Linux | thunderbird-mozsymbols Ubuntu 20.04 LTS (focal) | 1:78.7.1+build1-0ubuntu0.20.04.1 | [thunderbird-mozsymbols 1:78.7.1+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-thunderbird-mozsymbols-1-78.7.1-build1-0ubuntu0.20.04.1.md) | Jan 25, 2021 | | Linux | xul-ext-calendar-timezones Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | [xul-ext-calendar-timezones 1:78.8.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-xul-ext-calendar-timezones-1-78.8.1-build1-0ubuntu0.18.04.1.md) | Apr 22, 2021 | | Linux | xul-ext-calendar-timezones Ubuntu 20.04 LTS (focal) | 1:78.7.1+build1-0ubuntu0.20.04.1 | [xul-ext-calendar-timezones 1:78.7.1+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-xul-ext-calendar-timezones-1-78.7.1-build1-0ubuntu0.20.04.1.md) | Jan 25, 2021 | | Linux | xul-ext-gdata-provider Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | [xul-ext-gdata-provider 1:78.8.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-xul-ext-gdata-provider-1-78.8.1-build1-0ubuntu0.18.04.1.md) | Apr 22, 2021 | | Linux | xul-ext-gdata-provider Ubuntu 20.04 LTS (focal) | 1:78.7.1+build1-0ubuntu0.20.04.1 | [xul-ext-gdata-provider 1:78.7.1+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-xul-ext-gdata-provider-1-78.7.1-build1-0ubuntu0.20.04.1.md) | Jan 25, 2021 | | Linux | xul-ext-lightning Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | [xul-ext-lightning 1:78.8.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-xul-ext-lightning-1-78.8.1-build1-0ubuntu0.18.04.1.md) | Apr 22, 2021 | | Linux | xul-ext-lightning Ubuntu 20.04 LTS (focal) | 1:78.7.1+build1-0ubuntu0.20.04.1 | [xul-ext-lightning 1:78.7.1+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-xul-ext-lightning-1-78.7.1-build1-0ubuntu0.20.04.1.md) | Jan 25, 2021 | --- Data as of 2026-11-08T00:53:09Z UTC. 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