# CVE-2019-9821: firefox: A use-after-free vulnerability can occur in AssertWorkerThread due to a race condition with shared workers

CVE-2019-9821 is fixed in 4 products on 1 platform, first by firefox 67.0+build2-0ubuntu0.18.04.1, released May 20, 2019. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2019-9821
- Priority: Routine
- CVSS: n/a (Medium)
- EPSS: 0.0085
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 20, 2019

## Description

A use-after-free vulnerability can occur in AssertWorkerThread due to a race condition with shared workers. This results in a potentially exploitable crash. This vulnerability affects Firefox < 67.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | firefox Ubuntu 18.04.6 LTS (bionic) | 67.0+build2-0ubuntu0.18.04.1 | [firefox 67.0+build2-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-67.0-build2-0ubuntu0.18.04.1.md) | May 20, 2019 |
| Linux | firefox-globalmenu Ubuntu 18.04.6 LTS (bionic) | 67.0+build2-0ubuntu0.18.04.1 | [firefox-globalmenu 67.0+build2-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-globalmenu-67.0-build2-0ubuntu0.18.04.1.md) | May 20, 2019 |
| Linux | firefox-mozsymbols Ubuntu 18.04.6 LTS (bionic) | 67.0+build2-0ubuntu0.18.04.1 | [firefox-mozsymbols 67.0+build2-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-mozsymbols-67.0-build2-0ubuntu0.18.04.1.md) | May 20, 2019 |
| Linux | firefox-testsuite Ubuntu 18.04.6 LTS (bionic) | 67.0+build2-0ubuntu0.18.04.1 | [firefox-testsuite 67.0+build2-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-testsuite-67.0-build2-0ubuntu0.18.04.1.md) | May 20, 2019 |

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