# CVE-2021-29972: Firefox ESR and 1 other: A use-after-free vulnerability was found via testing, and traced to an out-of-date Cairo library.

CVE-2021-29972 is fixed in 4 products on 2 platforms, first by firefox 90.0+build1-0ubuntu0.18.04.1, released July 14, 2021. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2021-29972
- Priority: High
- CVSS: 8.8 (Medium)
- EPSS: 0.0104
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 14, 2021
- Vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2021-29972

## Description

A use-after-free vulnerability was found via testing, and traced to an out-of-date Cairo library. Updating the library resolved the issue, and may have remediated other, unknown security vulnerabilities as well. This vulnerability affects Firefox < 90.

## 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) | 90.0+build1-0ubuntu0.18.04.1 | [firefox 90.0+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-90.0-build1-0ubuntu0.18.04.1.md) | Jul 14, 2021 |
| Linux | firefox Ubuntu 20.04 LTS (focal) | 90.0+build1-0ubuntu0.20.04.1 | [firefox 90.0+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-90.0-build1-0ubuntu0.20.04.1.md) | Jul 14, 2021 |
| Linux | firefox-geckodriver Ubuntu 18.04.6 LTS (bionic) | 90.0+build1-0ubuntu0.18.04.1 | [firefox-geckodriver 90.0+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-geckodriver-90.0-build1-0ubuntu0.18.04.1.md) | Jul 14, 2021 |
| Linux | firefox-geckodriver Ubuntu 20.04 LTS (focal) | 90.0+build1-0ubuntu0.20.04.1 | [firefox-geckodriver 90.0+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-geckodriver-90.0-build1-0ubuntu0.20.04.1.md) | Jul 14, 2021 |
| Linux | firefox-mozsymbols Ubuntu 18.04.6 LTS (bionic) | 90.0+build1-0ubuntu0.18.04.1 | [firefox-mozsymbols 90.0+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-mozsymbols-90.0-build1-0ubuntu0.18.04.1.md) | Jul 14, 2021 |
| Linux | firefox-mozsymbols Ubuntu 20.04 LTS (focal) | 90.0+build1-0ubuntu0.20.04.1 | [firefox-mozsymbols 90.0+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-mozsymbols-90.0-build1-0ubuntu0.20.04.1.md) | Jul 14, 2021 |

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Data as of 2026-11-08T13:06:02Z 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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