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.
| Link | Tags |
|---|---|
| https://www.mozilla.org/security/advisories/mfsa2021-49/ | vendor advisory |
| https://www.mozilla.org/security/advisories/mfsa2021-50/ | vendor advisory |
| https://www.mozilla.org/security/advisories/mfsa2021-48/ | vendor advisory |
| https://bugzilla.mozilla.org/show_bug.cgi?id=1730935 | vendor advisory issue tracking permissions required |
| https://www.debian.org/security/2021/dsa-5026 | third party advisory vendor advisory |
| https://lists.debian.org/debian-lts-announce/2021/12/msg00030.html | third party advisory mailing list |
| https://www.debian.org/security/2022/dsa-5034 | third party advisory vendor advisory |
| https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html | third party advisory mailing list |
| https://security.gentoo.org/glsa/202202-03 | third party advisory vendor advisory |
| https://security.gentoo.org/glsa/202208-14 | third party advisory vendor advisory |