Medium (4.7). EPSS 1.1% chance of exploitation in the next 30 days.
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.
Severity
CVSS 3.1
4.7 medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N
EPSS
1.1% chance of exploitation in the next 30 days; higher than 66% of CVEs (scores of 2026-10-31)