CVE ID:	CVE-2021-38507
Description:	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.
Test IDs:	None available
Cross References:	Common Vulnerability Exposure (CVE) ID: CVE-2021-38507 Debian Security Information: DSA-5026 (Google Search) https://www.debian.org/security/2021/dsa-5026 Debian Security Information: DSA-5034 (Google Search) https://www.debian.org/security/2022/dsa-5034 https://security.gentoo.org/glsa/202202-03 https://security.gentoo.org/glsa/202208-14 https://bugzilla.mozilla.org/show_bug.cgi?id=1730935 https://bugzilla.mozilla.org/show_bug.cgi?id=1730935 https://www.mozilla.org/security/advisories/mfsa2021-48/ https://www.mozilla.org/security/advisories/mfsa2021-48/ https://www.mozilla.org/security/advisories/mfsa2021-49/ https://www.mozilla.org/security/advisories/mfsa2021-49/ https://www.mozilla.org/security/advisories/mfsa2021-50/ https://www.mozilla.org/security/advisories/mfsa2021-50/ https://lists.debian.org/debian-lts-announce/2021/12/msg00030.html https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html