# CVE-2019-11763: Firefox ESR: Failure to correctly handle null bytes when processing HTML entities resulted in Firefox incorrectly…

CVE-2019-11763 is fixed in 10 products on 2 platforms, first by thunderbird 1:68.2.1+build1-0ubuntu0.18.04.1, released October 22, 2019. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2019-11763
- Priority: Urgent
- CVSS: 6.1 (Critical)
- EPSS: 0.0115
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 22, 2019
- Vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2019-11763

## Description

Failure to correctly handle null bytes when processing HTML entities resulted in Firefox incorrectly parsing these entities. This could have led to HTML comment text being treated as HTML which could have led to XSS in a web application under certain conditions. It could have also led to HTML entities being masked from filters - enabling the use of entities to mask the actual characters of interest from filters. This vulnerability affects Firefox < 70, Thunderbird < 68.2, and Firefox ESR < 68.2.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Windows apps | Mozilla Firefox ESR (en-US) | 78.0esr | [Mozilla Firefox ESR (en-US) 78.0esr](https://patchblox.com/security/data/fix/windows-app/mozilla.firefox.esr-78.0esr.md) | Jun 25, 2020 |
| Linux | firefox RHEL 8 | 0:68.2.0-2.el8_0 | [RHSA-2019:3196](https://patchblox.com/security/data/fix/linux/rhsa-2019-3196.md) | Oct 24, 2019 |
| Linux | firefox Ubuntu 18.04.6 LTS (bionic) | 70.0+build2-0ubuntu0.18.04.1 | [firefox 70.0+build2-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-70.0-build2-0ubuntu0.18.04.1.md) | Jul 9, 2020 |
| Linux | firefox Ubuntu 20.04 LTS (focal) | 70.0+build2-0ubuntu1 | [firefox 70.0+build2-0ubuntu1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-70.0-build2-0ubuntu1.md) | Jul 9, 2020 |
| Linux | firefox ol 8 | 0:68.2.0-2.0.1.el8_0 | [ELSA-2019-3196](https://patchblox.com/security/data/fix/linux/elsa-2019-3196.md) | Oct 24, 2019 |
| Linux | firefox-geckodriver Ubuntu 18.04.6 LTS (bionic) | 70.0+build2-0ubuntu0.18.04.1 | [firefox-geckodriver 70.0+build2-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-geckodriver-70.0-build2-0ubuntu0.18.04.1.md) | Jul 9, 2020 |
| Linux | firefox-geckodriver Ubuntu 20.04 LTS (focal) | 70.0+build2-0ubuntu1 | [firefox-geckodriver 70.0+build2-0ubuntu1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-geckodriver-70.0-build2-0ubuntu1.md) | Jul 9, 2020 |
| Linux | firefox-mozsymbols Ubuntu 18.04.6 LTS (bionic) | 70.0+build2-0ubuntu0.18.04.1 | [firefox-mozsymbols 70.0+build2-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-mozsymbols-70.0-build2-0ubuntu0.18.04.1.md) | Jul 9, 2020 |
| Linux | firefox-mozsymbols Ubuntu 20.04 LTS (focal) | 70.0+build2-0ubuntu1 | [firefox-mozsymbols 70.0+build2-0ubuntu1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-mozsymbols-70.0-build2-0ubuntu1.md) | Jul 9, 2020 |
| Linux | thunderbird RHEL 8 | 0:68.2.0-1.el8_0 | [RHSA-2019:3237](https://patchblox.com/security/data/fix/linux/rhsa-2019-3237.md) | Oct 29, 2019 |
| Linux | thunderbird Ubuntu 18.04.6 LTS (bionic) | 1:68.2.1+build1-0ubuntu0.18.04.1 | [thunderbird 1:68.2.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-thunderbird-1-68.2.1-build1-0ubuntu0.18.04.1.md) | Oct 22, 2019 |
| Linux | thunderbird ol 8 | 0:68.2.0-1.0.1.el8_0 | [ELSA-2019-3237](https://patchblox.com/security/data/fix/linux/elsa-2019-3237.md) | Oct 30, 2019 |
| Linux | thunderbird-gnome-support Ubuntu 18.04.6 LTS (bionic) | 1:68.2.1+build1-0ubuntu0.18.04.1 | [thunderbird-gnome-support 1:68.2.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-thunderbird-gnome-support-1-68.2.1-build1-0ubuntu0.18.04.1.md) | Oct 22, 2019 |
| Linux | thunderbird-mozsymbols Ubuntu 18.04.6 LTS (bionic) | 1:68.2.1+build1-0ubuntu0.18.04.1 | [thunderbird-mozsymbols 1:68.2.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-thunderbird-mozsymbols-1-68.2.1-build1-0ubuntu0.18.04.1.md) | Oct 22, 2019 |
| Linux | xul-ext-calendar-timezones Ubuntu 18.04.6 LTS (bionic) | 1:68.2.1+build1-0ubuntu0.18.04.1 | [xul-ext-calendar-timezones 1:68.2.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-xul-ext-calendar-timezones-1-68.2.1-build1-0ubuntu0.18.04.1.md) | Oct 22, 2019 |
| Linux | xul-ext-gdata-provider Ubuntu 18.04.6 LTS (bionic) | 1:68.2.1+build1-0ubuntu0.18.04.1 | [xul-ext-gdata-provider 1:68.2.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-xul-ext-gdata-provider-1-68.2.1-build1-0ubuntu0.18.04.1.md) | Oct 22, 2019 |
| Linux | xul-ext-lightning Ubuntu 18.04.6 LTS (bionic) | 1:68.2.1+build1-0ubuntu0.18.04.1 | [xul-ext-lightning 1:68.2.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-xul-ext-lightning-1-68.2.1-build1-0ubuntu0.18.04.1.md) | Oct 22, 2019 |

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