The HTTP Alternative Services header, Alt-Svc, can be used by a malicious site to scan all TCP ports of any host that the accessible to a user when web content is loaded. This vulnerability affects Firefox < 68.
https://www.mozilla.org/security/advisories/mfsa2019-21/
https://bugzilla.mozilla.org/show_bug.cgi?id=1552993
https://security.gentoo.org/glsa/201908-12
http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00009.html
http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00010.html
http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00011.html
http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00017.html
Source: MITRE
Published: 2019-07-23
Updated: 2023-01-31
Type: CWE-668
Base Score: 4.3
Vector: AV:N/AC:M/Au:N/C:P/I:N/A:N
Impact Score: 2.9
Exploitability Score: 8.6
Severity: MEDIUM
Base Score: 4.7
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N
Impact Score: 1.4
Exploitability Score: 2.8
Severity: MEDIUM