Mozilla Firefox ESR and 3 others: The Opportunistic Encryption feature of HTTP2 (RFC 8164) allows a connection to be transparently upgraded…
CVE-2021-38507 is fixed in 12 products on 2 platforms, first by Mozilla Thunderbird (en-US) 91.3.0, released November 1, 2021. It is not reported as exploited. Patch Radar priority: High.
The Opportunistic Encryption feature of HTTP2 (RFC 8164) allows a connection to be transparently upgraded to TLS while retaining the visual properties of an HTTP connection, including being same-origin with unencrypted connections on port 80. However, if a second encrypted port on the same IP address (e.g. port 8443) did not opt-in to opportunistic encryption; a network attacker could forward a connection from the browser to port 443 to port 8443, causing the browser to treat the content of port 8443 as same-origin with HTTP. This was resolved by disabling the Opportunistic Encryption feature, which had low usage. This vulnerability affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Windows apps | |||
| Mozilla Firefox ESR (en-US) | 102.0 | Mozilla Firefox ESR (en-US) 102.0 | Jun 23, 2022 |
| Mozilla Thunderbird (en-US) | 91.3.0 | Mozilla Thunderbird (en-US) 91.3.0 | Nov 1, 2021 |
| Linux | |||
| firefox · RHEL 8 | 0:91.3.0-1.el8_4 | RHSA-2021:4123 | Nov 3, 2021 |
| firefox · Ubuntu 18.04.6 LTS (bionic) | 94.0+build3-0ubuntu0.18.04.1 | firefox 94.0+build3-0ubuntu0.18.04.1 | Nov 2, 2021 |
| firefox · Ubuntu 20.04 LTS (focal) | 94.0+build3-0ubuntu0.20.04.1 | firefox 94.0+build3-0ubuntu0.20.04.1 | Nov 2, 2021 |
| firefox · Ubuntu 22.04.1 LTS (jammy) | 94.0+build3-0ubuntu1 | firefox 94.0+build3-0ubuntu1 | Nov 2, 2021 |
| firefox · ol 8 | 0:91.3.0-1.0.1.el8_4 | ELSA-2021-4123 | Nov 4, 2021 |
| firefox-esr · Debian 12.15 (bookworm) | 91.3.0esr-1 | DEBIAN-CVE-2021-38507 | Dec 8, 2021 |
| firefox-esr · Debian 13.5 (trixie) | 91.3.0esr-1 | DEBIAN-CVE-2021-38507 | Dec 8, 2021 |
| firefox-esr · Debian 14 | 91.3.0esr-1 | DEBIAN-CVE-2021-38507 | Dec 8, 2021 |
| firefox-geckodriver · Ubuntu 18.04.6 LTS (bionic) | 94.0+build3-0ubuntu0.18.04.1 | firefox-geckodriver 94.0+build3-0ubuntu0.18.04.1 | Nov 2, 2021 |
| firefox-geckodriver · Ubuntu 20.04 LTS (focal) | 94.0+build3-0ubuntu0.20.04.1 | firefox-geckodriver 94.0+build3-0ubuntu0.20.04.1 | Nov 2, 2021 |
| firefox-geckodriver · Ubuntu 22.04.1 LTS (jammy) | 94.0+build3-0ubuntu1 | firefox-geckodriver 94.0+build3-0ubuntu1 | Nov 2, 2021 |
| firefox-mozsymbols · Ubuntu 18.04.6 LTS (bionic) | 94.0+build3-0ubuntu0.18.04.1 | firefox-mozsymbols 94.0+build3-0ubuntu0.18.04.1 | Nov 2, 2021 |
| firefox-mozsymbols · Ubuntu 20.04 LTS (focal) | 94.0+build3-0ubuntu0.20.04.1 | firefox-mozsymbols 94.0+build3-0ubuntu0.20.04.1 | Nov 2, 2021 |
| firefox-mozsymbols · Ubuntu 22.04.1 LTS (jammy) | 94.0+build3-0ubuntu1 | firefox-mozsymbols 94.0+build3-0ubuntu1 | Nov 2, 2021 |
| thunderbird · Debian 12.15 (bookworm) | 1:91.3.0-1 | DEBIAN-CVE-2021-38507 | Dec 8, 2021 |
| thunderbird · Debian 13.5 (trixie) | 1:91.3.0-1 | DEBIAN-CVE-2021-38507 | Dec 8, 2021 |
| thunderbird · Debian 14 | 1:91.3.0-1 | DEBIAN-CVE-2021-38507 | Dec 8, 2021 |
| thunderbird · RHEL 8 | 0:91.3.0-2.el8_4 | RHSA-2021:4130 | Nov 4, 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 · Ubuntu 22.04.1 LTS (jammy) | 1:91.3.1+build1-0ubuntu1 | thunderbird 1:91.3.1+build1-0ubuntu1 | Nov 2, 2021 |
| thunderbird · ol 8 | 0:91.3.0-2.0.1.el8_4 | ELSA-2021-4130 | Nov 5, 2021 |
| 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-gnome-support · Ubuntu 22.04.1 LTS (jammy) | 1:91.3.1+build1-0ubuntu1 | thunderbird-gnome-support 1:91.3.1+build1-0ubuntu1 | Nov 2, 2021 |
| 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 |
| thunderbird-mozsymbols · Ubuntu 22.04.1 LTS (jammy) | 1:91.3.1+build1-0ubuntu1 | thunderbird-mozsymbols 1:91.3.1+build1-0ubuntu1 | Nov 2, 2021 |
| 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-calendar-timezones · Ubuntu 22.04.1 LTS (jammy) | 1:91.3.1+build1-0ubuntu1 | xul-ext-calendar-timezones 1:91.3.1+build1-0ubuntu1 | Nov 2, 2021 |
| 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-gdata-provider · Ubuntu 22.04.1 LTS (jammy) | 1:91.3.1+build1-0ubuntu1 | xul-ext-gdata-provider 1:91.3.1+build1-0ubuntu1 | Nov 2, 2021 |
| 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 |
| xul-ext-lightning · Ubuntu 22.04.1 LTS (jammy) | 1:91.3.1+build1-0ubuntu1 | xul-ext-lightning 1:91.3.1+build1-0ubuntu1 | Nov 2, 2021 |
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