{"id":"ALPINE-CVE-2021-38507","details":"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 \u003c 94, Thunderbird \u003c 91.3, and Firefox ESR \u003c 91.3.","modified":"2026-11-03T06:32:58.579941406Z","published":"2021-12-08T22:15:08.947Z","upstream":["CVE-2021-38507"],"references":[{"type":"ADVISORY","url":"https://security.alpinelinux.org/vuln/CVE-2021-38507"}],"affected":[{"package":{"name":"firefox","ecosystem":"Alpine:v3.15","purl":"pkg:apk/alpine/firefox?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"94.0-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-38507.json"}},{"package":{"name":"firefox","ecosystem":"Alpine:v3.16","purl":"pkg:apk/alpine/firefox?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"94.0-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-38507.json"}},{"package":{"name":"firefox","ecosystem":"Alpine:v3.17","purl":"pkg:apk/alpine/firefox?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"94.0-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-38507.json"}},{"package":{"name":"firefox","ecosystem":"Alpine:v3.18","purl":"pkg:apk/alpine/firefox?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"94.0-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-38507.json"}},{"package":{"name":"firefox","ecosystem":"Alpine:v3.19","purl":"pkg:apk/alpine/firefox?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"94.0-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-38507.json"}},{"package":{"name":"firefox","ecosystem":"Alpine:v3.20","purl":"pkg:apk/alpine/firefox?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"94.0-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-38507.json"}},{"package":{"name":"firefox","ecosystem":"Alpine:v3.21","purl":"pkg:apk/alpine/firefox?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"94.0-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-38507.json"}},{"package":{"name":"firefox","ecosystem":"Alpine:v3.22","purl":"pkg:apk/alpine/firefox?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"94.0-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-38507.json"}},{"package":{"name":"firefox","ecosystem":"Alpine:v3.23","purl":"pkg:apk/alpine/firefox?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"94.0-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-38507.json"}},{"package":{"name":"firefox-esr","ecosystem":"Alpine:v3.15","purl":"pkg:apk/alpine/firefox-esr?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"91.3.0-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-38507.json"}},{"package":{"name":"firefox-esr","ecosystem":"Alpine:v3.16","purl":"pkg:apk/alpine/firefox-esr?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"91.3.0-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-38507.json"}},{"package":{"name":"firefox-esr","ecosystem":"Alpine:v3.17","purl":"pkg:apk/alpine/firefox-esr?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"91.3.0-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-38507.json"}},{"package":{"name":"firefox-esr","ecosystem":"Alpine:v3.18","purl":"pkg:apk/alpine/firefox-esr?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"91.3.0-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-38507.json"}},{"package":{"name":"firefox-esr","ecosystem":"Alpine:v3.19","purl":"pkg:apk/alpine/firefox-esr?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"91.3.0-r0"}]}],"ecosystem_specific":{},"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2021-38507.json"}},{"package":{"name":"firefox-esr","ecosystem":"Alpine:v3.20","purl":"pkg:apk/alpine/firefox-esr?arch=source"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fi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