# CVE-2021-38501: Mozilla Firefox ESR and 3 others: Mozilla developers reported memory safety bugs present in Firefox 92 and Firefox ESR 91.1.

CVE-2021-38501 is fixed in 11 products on 2 platforms, first by Mozilla Thunderbird (en-US) 91.2.0, released October 4, 2021. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2021-38501
- Priority: High
- CVSS: 8.8 (Important)
- EPSS: 0.0105
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 11, 2021
- Vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2021-38501

## Description

Mozilla developers reported memory safety bugs present in Firefox 92 and Firefox ESR 91.1. 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 < 93, Thunderbird < 91.2, and Firefox ESR < 91.2.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Windows apps | Mozilla Firefox ESR (en-US) | 102.0 | [Mozilla Firefox ESR (en-US) 102.0](https://patchblox.com/security/data/fix/windows-app/mozilla.firefox.esr-102.0.md) | Jun 23, 2022 |
| Windows apps | Mozilla Thunderbird (en-US) | 91.2.0 | [Mozilla Thunderbird (en-US) 91.2.0](https://patchblox.com/security/data/fix/windows-app/mozilla.thunderbird-91.2.0.md) | Oct 4, 2021 |
| Linux | firefox RHEL 8 | 0:91.2.0-4.el8_4 | [RHSA-2021:3755](https://patchblox.com/security/data/fix/linux/rhsa-2021-3755.md) | Oct 11, 2021 |
| Linux | firefox Ubuntu 18.04.6 LTS (bionic) | 93.0+build1-0ubuntu0.18.04.1 | [firefox 93.0+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-93.0-build1-0ubuntu0.18.04.1.md) | Nov 2, 2021 |
| Linux | firefox Ubuntu 20.04 LTS (focal) | 93.0+build1-0ubuntu0.20.04.1 | [firefox 93.0+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-93.0-build1-0ubuntu0.20.04.1.md) | Nov 2, 2021 |
| Linux | firefox ol 8 | 0:91.2.0-4.0.1.el8_4 | [ELSA-2021-3755](https://patchblox.com/security/data/fix/linux/elsa-2021-3755.md) | Oct 11, 2021 |
| Linux | firefox-geckodriver Ubuntu 18.04.6 LTS (bionic) | 93.0+build1-0ubuntu0.18.04.1 | [firefox-geckodriver 93.0+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-geckodriver-93.0-build1-0ubuntu0.18.04.1.md) | Nov 2, 2021 |
| Linux | firefox-geckodriver Ubuntu 20.04 LTS (focal) | 93.0+build1-0ubuntu0.20.04.1 | [firefox-geckodriver 93.0+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-geckodriver-93.0-build1-0ubuntu0.20.04.1.md) | Nov 2, 2021 |
| Linux | firefox-mozsymbols Ubuntu 18.04.6 LTS (bionic) | 93.0+build1-0ubuntu0.18.04.1 | [firefox-mozsymbols 93.0+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-mozsymbols-93.0-build1-0ubuntu0.18.04.1.md) | Nov 2, 2021 |
| Linux | firefox-mozsymbols Ubuntu 20.04 LTS (focal) | 93.0+build1-0ubuntu0.20.04.1 | [firefox-mozsymbols 93.0+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-mozsymbols-93.0-build1-0ubuntu0.20.04.1.md) | Nov 2, 2021 |
| Linux | thunderbird RHEL 8 | 0:91.2.0-1.el8_4 | [RHSA-2021:3838](https://patchblox.com/security/data/fix/linux/rhsa-2021-3838.md) | Oct 13, 2021 |
| Linux | thunderbird Ubuntu 18.04.6 LTS (bionic) | 1:91.5.0+build1-0ubuntu0.18.04.1 | [thunderbird 1:91.5.0+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-thunderbird-1-91.5.0-build1-0ubuntu0.18.04.1.md) | Feb 16, 2023 |
| Linux | thunderbird Ubuntu 20.04 LTS (focal) | 1:91.5.0+build1-0ubuntu0.20.04.1 | [thunderbird 1:91.5.0+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-thunderbird-1-91.5.0-build1-0ubuntu0.20.04.1.md) | Feb 16, 2023 |
| Linux | thunderbird Ubuntu 22.04.1 LTS (jammy) | 1:91.3.0+build2-0ubuntu1 | [thunderbird 1:91.3.0+build2-0ubuntu1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-thunderbird-1-91.3.0-build2-0ubuntu1.md) | Nov 2, 2021 |
| Linux | thunderbird ol 8 | 0:91.2.0-1.0.1.el8_4 | [ELSA-2021-3838](https://patchblox.com/security/data/fix/linux/elsa-2021-3838.md) | Oct 15, 2021 |
| Linux | thunderbird-gnome-support Ubuntu 18.04.6 LTS (bionic) | 1:91.5.0+build1-0ubuntu0.18.04.1 | [thunderbird-gnome-support 1:91.5.0+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-thunderbird-gnome-support-1-91.5.0-build1-0ubuntu0.18.04.1.md) | Feb 16, 2023 |
| Linux | thunderbird-gnome-support Ubuntu 20.04 LTS (focal) | 1:91.5.0+build1-0ubuntu0.20.04.1 | [thunderbird-gnome-support 1:91.5.0+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-thunderbird-gnome-support-1-91.5.0-build1-0ubuntu0.20.04.1.md) | Feb 16, 2023 |
| Linux | thunderbird-gnome-support Ubuntu 22.04.1 LTS (jammy) | 1:91.3.0+build2-0ubuntu1 | [thunderbird-gnome-support 1:91.3.0+build2-0ubuntu1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-thunderbird-gnome-support-1-91.3.0-build2-0ubuntu1.md) | Nov 2, 2021 |
| Linux | thunderbird-mozsymbols Ubuntu 18.04.6 LTS (bionic) | 1:91.5.0+build1-0ubuntu0.18.04.1 | [thunderbird-mozsymbols 1:91.5.0+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-thunderbird-mozsymbols-1-91.5.0-build1-0ubuntu0.18.04.1.md) | Feb 16, 2023 |
| Linux | thunderbird-mozsymbols Ubuntu 20.04 LTS (focal) | 1:91.5.0+build1-0ubuntu0.20.04.1 | [thunderbird-mozsymbols 1:91.5.0+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-thunderbird-mozsymbols-1-91.5.0-build1-0ubuntu0.20.04.1.md) | Feb 16, 2023 |
| Linux | thunderbird-mozsymbols Ubuntu 22.04.1 LTS (jammy) | 1:91.3.0+build2-0ubuntu1 | [thunderbird-mozsymbols 1:91.3.0+build2-0ubuntu1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-thunderbird-mozsymbols-1-91.3.0-build2-0ubuntu1.md) | Nov 2, 2021 |
| Linux | xul-ext-calendar-timezones Ubuntu 18.04.6 LTS (bionic) | 1:91.5.0+build1-0ubuntu0.18.04.1 | [xul-ext-calendar-timezones 1:91.5.0+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-xul-ext-calendar-timezones-1-91.5.0-build1-0ubuntu0.18.04.1.md) | Feb 16, 2023 |
| Linux | xul-ext-calendar-timezones Ubuntu 20.04 LTS (focal) | 1:91.5.0+build1-0ubuntu0.20.04.1 | [xul-ext-calendar-timezones 1:91.5.0+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-xul-ext-calendar-timezones-1-91.5.0-build1-0ubuntu0.20.04.1.md) | Feb 16, 2023 |
| Linux | xul-ext-calendar-timezones Ubuntu 22.04.1 LTS (jammy) | 1:91.3.0+build2-0ubuntu1 | [xul-ext-calendar-timezones 1:91.3.0+build2-0ubuntu1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-xul-ext-calendar-timezones-1-91.3.0-build2-0ubuntu1.md) | Nov 2, 2021 |
| Linux | xul-ext-gdata-provider Ubuntu 18.04.6 LTS (bionic) | 1:91.5.0+build1-0ubuntu0.18.04.1 | [xul-ext-gdata-provider 1:91.5.0+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-xul-ext-gdata-provider-1-91.5.0-build1-0ubuntu0.18.04.1.md) | Feb 16, 2023 |
| Linux | xul-ext-gdata-provider Ubuntu 20.04 LTS (focal) | 1:91.5.0+build1-0ubuntu0.20.04.1 | [xul-ext-gdata-provider 1:91.5.0+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-xul-ext-gdata-provider-1-91.5.0-build1-0ubuntu0.20.04.1.md) | Feb 16, 2023 |
| Linux | xul-ext-gdata-provider Ubuntu 22.04.1 LTS (jammy) | 1:91.3.0+build2-0ubuntu1 | [xul-ext-gdata-provider 1:91.3.0+build2-0ubuntu1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-xul-ext-gdata-provider-1-91.3.0-build2-0ubuntu1.md) | Nov 2, 2021 |
| Linux | xul-ext-lightning Ubuntu 18.04.6 LTS (bionic) | 1:91.5.0+build1-0ubuntu0.18.04.1 | [xul-ext-lightning 1:91.5.0+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-xul-ext-lightning-1-91.5.0-build1-0ubuntu0.18.04.1.md) | Feb 16, 2023 |
| Linux | xul-ext-lightning Ubuntu 20.04 LTS (focal) | 1:91.5.0+build1-0ubuntu0.20.04.1 | [xul-ext-lightning 1:91.5.0+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-xul-ext-lightning-1-91.5.0-build1-0ubuntu0.20.04.1.md) | Feb 16, 2023 |
| Linux | xul-ext-lightning Ubuntu 22.04.1 LTS (jammy) | 1:91.3.0+build2-0ubuntu1 | [xul-ext-lightning 1:91.3.0+build2-0ubuntu1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-xul-ext-lightning-1-91.3.0-build2-0ubuntu1.md) | Nov 2, 2021 |

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