Firefox ESR and 3 others: Firefox incorrectly accepted a newline in a HTTP/3 header, interpretting it as two separate headers.
CVE-2021-29991 is fixed in 11 products on 2 platforms, first by firefox 91.0.1+build1-0ubuntu0.18.04.1, released August 17, 2021. It is not reported as exploited. Patch Radar priority: High.
Firefox incorrectly accepted a newline in a HTTP/3 header, interpretting it as two separate headers. This allowed for a header splitting attack against servers using HTTP/3. This vulnerability affects Firefox < 91.0.1 and Thunderbird < 91.0.1.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Windows apps | |||
| Mozilla Firefox ESR (en-US) | 91.3.0 | Mozilla Firefox ESR (en-US) 91.3.0 | Oct 28, 2021 |
| Mozilla Thunderbird (en-US) | 91.0.3 | Mozilla Thunderbird (en-US) 91.0.3 | Aug 24, 2021 |
| Linux | |||
| firefox · Ubuntu 18.04.6 LTS (bionic) | 91.0.1+build1-0ubuntu0.18.04.1 | firefox 91.0.1+build1-0ubuntu0.18.04.1 | Aug 17, 2021 |
| firefox · Ubuntu 20.04 LTS (focal) | 91.0.1+build1-0ubuntu0.20.04.1 | firefox 91.0.1+build1-0ubuntu0.20.04.1 | Aug 17, 2021 |
| firefox-geckodriver · Ubuntu 18.04.6 LTS (bionic) | 91.0.1+build1-0ubuntu0.18.04.1 | firefox-geckodriver 91.0.1+build1-0ubuntu0.18.04.1 | Aug 17, 2021 |
| firefox-geckodriver · Ubuntu 20.04 LTS (focal) | 91.0.1+build1-0ubuntu0.20.04.1 | firefox-geckodriver 91.0.1+build1-0ubuntu0.20.04.1 | Aug 17, 2021 |
| firefox-mozsymbols · Ubuntu 18.04.6 LTS (bionic) | 91.0.1+build1-0ubuntu0.18.04.1 | firefox-mozsymbols 91.0.1+build1-0ubuntu0.18.04.1 | Aug 17, 2021 |
| firefox-mozsymbols · Ubuntu 20.04 LTS (focal) | 91.0.1+build1-0ubuntu0.20.04.1 | firefox-mozsymbols 91.0.1+build1-0ubuntu0.20.04.1 | Aug 17, 2021 |
| thunderbird · Ubuntu 18.04.6 LTS (bionic) | 1:91.5.0+build1-0ubuntu0.18.04.1 | thunderbird 1:91.5.0+build1-0ubuntu0.18.04.1 | Feb 16, 2023 |
| thunderbird · Ubuntu 20.04 LTS (focal) | 1:91.5.0+build1-0ubuntu0.20.04.1 | thunderbird 1:91.5.0+build1-0ubuntu0.20.04.1 | Feb 16, 2023 |
| thunderbird-gnome-support · Ubuntu 18.04.6 LTS (bionic) | 1:91.5.0+build1-0ubuntu0.18.04.1 | thunderbird-gnome-support 1:91.5.0+build1-0ubuntu0.18.04.1 | Feb 16, 2023 |
| thunderbird-gnome-support · Ubuntu 20.04 LTS (focal) | 1:91.5.0+build1-0ubuntu0.20.04.1 | thunderbird-gnome-support 1:91.5.0+build1-0ubuntu0.20.04.1 | Feb 16, 2023 |
| thunderbird-mozsymbols · Ubuntu 18.04.6 LTS (bionic) | 1:91.5.0+build1-0ubuntu0.18.04.1 | thunderbird-mozsymbols 1:91.5.0+build1-0ubuntu0.18.04.1 | Feb 16, 2023 |
| thunderbird-mozsymbols · Ubuntu 20.04 LTS (focal) | 1:91.5.0+build1-0ubuntu0.20.04.1 | thunderbird-mozsymbols 1:91.5.0+build1-0ubuntu0.20.04.1 | Feb 16, 2023 |
| xul-ext-calendar-timezones · Ubuntu 18.04.6 LTS (bionic) | 1:91.5.0+build1-0ubuntu0.18.04.1 | xul-ext-calendar-timezones 1:91.5.0+build1-0ubuntu0.18.04.1 | Feb 16, 2023 |
| xul-ext-calendar-timezones · Ubuntu 20.04 LTS (focal) | 1:91.5.0+build1-0ubuntu0.20.04.1 | xul-ext-calendar-timezones 1:91.5.0+build1-0ubuntu0.20.04.1 | Feb 16, 2023 |
| xul-ext-gdata-provider · Ubuntu 18.04.6 LTS (bionic) | 1:91.5.0+build1-0ubuntu0.18.04.1 | xul-ext-gdata-provider 1:91.5.0+build1-0ubuntu0.18.04.1 | Feb 16, 2023 |
| xul-ext-gdata-provider · Ubuntu 20.04 LTS (focal) | 1:91.5.0+build1-0ubuntu0.20.04.1 | xul-ext-gdata-provider 1:91.5.0+build1-0ubuntu0.20.04.1 | Feb 16, 2023 |
| xul-ext-lightning · Ubuntu 18.04.6 LTS (bionic) | 1:91.5.0+build1-0ubuntu0.18.04.1 | xul-ext-lightning 1:91.5.0+build1-0ubuntu0.18.04.1 | Feb 16, 2023 |
| xul-ext-lightning · Ubuntu 20.04 LTS (focal) | 1:91.5.0+build1-0ubuntu0.20.04.1 | xul-ext-lightning 1:91.5.0+build1-0ubuntu0.20.04.1 | Feb 16, 2023 |
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