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.
The product does not properly verify that the source of data or communication is valid.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Firefox | Mozilla | * | 94.0 (excluding) |
| Firefox_esr | Mozilla | * | 91.3.0 (excluding) |
| Thunderbird | Mozilla | * | 91.3.0 (excluding) |
| Red Hat Enterprise Linux 7 | RedHat | firefox-0:91.3.0-1.el7_9 | * |
| Red Hat Enterprise Linux 7 | RedHat | thunderbird-0:91.3.0-2.el7_9 | * |
| Red Hat Enterprise Linux 8 | RedHat | firefox-0:91.3.0-1.el8_4 | * |
| Red Hat Enterprise Linux 8 | RedHat | thunderbird-0:91.3.0-2.el8_4 | * |
| Red Hat Enterprise Linux 8.1 Extended Update Support | RedHat | thunderbird-0:91.3.0-2.el8_1 | * |
| Red Hat Enterprise Linux 8.1 Extended Update Support | RedHat | firefox-0:91.3.0-1.el8_1 | * |
| Red Hat Enterprise Linux 8.2 Extended Update Support | RedHat | thunderbird-0:91.3.0-2.el8_2 | * |
| Red Hat Enterprise Linux 8.2 Extended Update Support | RedHat | firefox-0:91.3.0-1.el8_2 | * |
| Firefox | Ubuntu | bionic | * |
| Firefox | Ubuntu | devel | * |
| Firefox | Ubuntu | focal | * |
| Firefox | Ubuntu | hirsute | * |
| Firefox | Ubuntu | impish | * |
| Firefox | Ubuntu | jammy | * |
| Firefox | Ubuntu | kinetic | * |
| Firefox | Ubuntu | lunar | * |
| Firefox | Ubuntu | mantic | * |
| Firefox | Ubuntu | noble | * |
| Firefox | Ubuntu | trusty | * |
| Firefox | Ubuntu | upstream | * |
| Firefox | Ubuntu | xenial | * |
| Mozjs38 | Ubuntu | bionic | * |
| Mozjs38 | Ubuntu | esm-apps/bionic | * |
| Mozjs38 | Ubuntu | upstream | * |
| Mozjs52 | Ubuntu | bionic | * |
| Mozjs52 | Ubuntu | esm-apps/focal | * |
| Mozjs52 | Ubuntu | esm-infra/bionic | * |
| Mozjs52 | Ubuntu | focal | * |
| Mozjs52 | Ubuntu | upstream | * |
| Mozjs68 | Ubuntu | focal | * |
| Mozjs68 | Ubuntu | upstream | * |
| Mozjs78 | Ubuntu | esm-apps/jammy | * |
| Mozjs78 | Ubuntu | hirsute | * |
| Mozjs78 | Ubuntu | impish | * |
| Mozjs78 | Ubuntu | jammy | * |
| Mozjs78 | Ubuntu | kinetic | * |
| Mozjs78 | Ubuntu | lunar | * |
| Mozjs78 | Ubuntu | upstream | * |
| Thunderbird | Ubuntu | bionic | * |
| Thunderbird | Ubuntu | devel | * |
| Thunderbird | Ubuntu | focal | * |
| Thunderbird | Ubuntu | hirsute | * |
| Thunderbird | Ubuntu | impish | * |
| Thunderbird | Ubuntu | jammy | * |
| Thunderbird | Ubuntu | kinetic | * |
| Thunderbird | Ubuntu | lunar | * |
| Thunderbird | Ubuntu | mantic | * |
| Thunderbird | Ubuntu | noble | * |
| Thunderbird | Ubuntu | trusty | * |
| Thunderbird | Ubuntu | upstream | * |
| Thunderbird | Ubuntu | xenial | * |