# CVE-2021-43540: Mozilla Firefox ESR and 1 other: WebExtensions with the correct permissions were able to create and install ServiceWorkers for third-party…

CVE-2021-43540 is fixed in 4 products on 2 platforms, first by firefox 95.0+build1-0ubuntu0.18.04.1, released December 7, 2021. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2021-43540
- Priority: Routine
- CVSS: 6.5 (Medium)
- EPSS: 0.0089
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Dec 7, 2021
- Vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2021-43540

## Description

WebExtensions with the correct permissions were able to create and install ServiceWorkers for third-party websites that would not have been uninstalled with the extension. This vulnerability affects Firefox < 95.

## 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 |
| Linux | firefox Ubuntu 18.04.6 LTS (bionic) | 95.0+build1-0ubuntu0.18.04.1 | [firefox 95.0+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-95.0-build1-0ubuntu0.18.04.1.md) | Dec 7, 2021 |
| Linux | firefox Ubuntu 20.04 LTS (focal) | 95.0+build1-0ubuntu0.20.04.1 | [firefox 95.0+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-95.0-build1-0ubuntu0.20.04.1.md) | Dec 7, 2021 |
| Linux | firefox Ubuntu 22.04.1 LTS (jammy) | 95.0+build1-0ubuntu1 | [firefox 95.0+build1-0ubuntu1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-firefox-95.0-build1-0ubuntu1.md) | Dec 7, 2021 |
| Linux | firefox-geckodriver Ubuntu 18.04.6 LTS (bionic) | 95.0+build1-0ubuntu0.18.04.1 | [firefox-geckodriver 95.0+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-geckodriver-95.0-build1-0ubuntu0.18.04.1.md) | Dec 7, 2021 |
| Linux | firefox-geckodriver Ubuntu 20.04 LTS (focal) | 95.0+build1-0ubuntu0.20.04.1 | [firefox-geckodriver 95.0+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-geckodriver-95.0-build1-0ubuntu0.20.04.1.md) | Dec 7, 2021 |
| Linux | firefox-geckodriver Ubuntu 22.04.1 LTS (jammy) | 95.0+build1-0ubuntu1 | [firefox-geckodriver 95.0+build1-0ubuntu1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-firefox-geckodriver-95.0-build1-0ubuntu1.md) | Dec 7, 2021 |
| Linux | firefox-mozsymbols Ubuntu 18.04.6 LTS (bionic) | 95.0+build1-0ubuntu0.18.04.1 | [firefox-mozsymbols 95.0+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-mozsymbols-95.0-build1-0ubuntu0.18.04.1.md) | Dec 7, 2021 |
| Linux | firefox-mozsymbols Ubuntu 20.04 LTS (focal) | 95.0+build1-0ubuntu0.20.04.1 | [firefox-mozsymbols 95.0+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-mozsymbols-95.0-build1-0ubuntu0.20.04.1.md) | Dec 7, 2021 |
| Linux | firefox-mozsymbols Ubuntu 22.04.1 LTS (jammy) | 95.0+build1-0ubuntu1 | [firefox-mozsymbols 95.0+build1-0ubuntu1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-firefox-mozsymbols-95.0-build1-0ubuntu1.md) | Dec 7, 2021 |

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