# CVE-2021-29990: Firefox ESR and 1 other: Mozilla developers and community members reported memory safety bugs present in Firefox 90.

CVE-2021-29990 is fixed in 4 products on 2 platforms, first by Mozilla Firefox ESR (en-US) 91.0, released August 4, 2021. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2021-29990
- Priority: High
- CVSS: 8.8 (Medium)
- EPSS: 0.0101
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 10, 2021
- Vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2021-29990

## Description

Mozilla developers and community members reported memory safety bugs present in Firefox 90. 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 < 91.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Windows apps | Mozilla Firefox ESR (en-US) | 91.0 | [Mozilla Firefox ESR (en-US) 91.0](https://patchblox.com/security/data/fix/windows-app/mozilla.firefox.esr-91.0.md) | Aug 4, 2021 |
| Linux | firefox Ubuntu 18.04.6 LTS (bionic) | 91.0+build2-0ubuntu0.18.04.1 | [firefox 91.0+build2-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-91.0-build2-0ubuntu0.18.04.1.md) | Aug 10, 2021 |
| Linux | firefox Ubuntu 20.04 LTS (focal) | 91.0+build2-0ubuntu0.20.04.1 | [firefox 91.0+build2-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-91.0-build2-0ubuntu0.20.04.1.md) | Aug 10, 2021 |
| Linux | firefox-geckodriver Ubuntu 18.04.6 LTS (bionic) | 91.0+build2-0ubuntu0.18.04.1 | [firefox-geckodriver 91.0+build2-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-geckodriver-91.0-build2-0ubuntu0.18.04.1.md) | Aug 10, 2021 |
| Linux | firefox-geckodriver Ubuntu 20.04 LTS (focal) | 91.0+build2-0ubuntu0.20.04.1 | [firefox-geckodriver 91.0+build2-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-geckodriver-91.0-build2-0ubuntu0.20.04.1.md) | Aug 10, 2021 |
| Linux | firefox-mozsymbols Ubuntu 18.04.6 LTS (bionic) | 91.0+build2-0ubuntu0.18.04.1 | [firefox-mozsymbols 91.0+build2-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-mozsymbols-91.0-build2-0ubuntu0.18.04.1.md) | Aug 10, 2021 |
| Linux | firefox-mozsymbols Ubuntu 20.04 LTS (focal) | 91.0+build2-0ubuntu0.20.04.1 | [firefox-mozsymbols 91.0+build2-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-mozsymbols-91.0-build2-0ubuntu0.20.04.1.md) | Aug 10, 2021 |

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Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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