DEBIAN-CVE-2021-38507
- Source
- https://security-tracker.debian.org/tracker/CVE-2021-38507
- Import Source
- https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2021-38507.json
- JSON Data
- https://api.test.osv.dev/v1/vulns/DEBIAN-CVE-2021-38507
- Upstream
- Downstream
- Published
- 2021-12-08T22:15:08Z
- Modified
- 2026-09-15T09:02:33Z
- Severity
-
- 6.5 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N CVSS Calculator
- Summary
- [none]
- 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 < 94, Thunderbird < 91.3, and Firefox ESR < 91.3.
- References
Affected packages
Debian:12
firefox-esr
Package
- Name
- firefox-esr
- Purl
- pkg:deb/debian/firefox-esr?arch=source&distro=bookworm
thunderbird
Package
- Name
- thunderbird
- Purl
- pkg:deb/debian/thunderbird?arch=source&distro=bookworm
Debian:13
firefox-esr
Package
- Name
- firefox-esr
- Purl
- pkg:deb/debian/firefox-esr?arch=source&distro=trixie
thunderbird
Package
- Name
- thunderbird
- Purl
- pkg:deb/debian/thunderbird?arch=source&distro=trixie
Debian:14
firefox-esr
Package
- Name
- firefox-esr
- Purl
- pkg:deb/debian/firefox-esr?arch=source&distro=forky
thunderbird
Package
- Name
- thunderbird
- Purl
- pkg:deb/debian/thunderbird?arch=source&distro=forky