CVE-2026-16375

Site isolation issue in the Networking: HTTP component

Critical · published July 21, 2026

CVSS v3.1
9.8
EPSS
0%
Percentile
10.6
In the wild
Unconfirmed
What it is

Site isolation issue in the Networking: HTTP component. This vulnerability was fixed in Firefox 153, Firefox ESR 140.13, Thunderbird 153, and Thunderbird 140.13.

The record
Technical detail
CVSS v3.1
9.8 · CRITICAL
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS v4.0
Not supplied
EPSS
0.00209 · 10.6th percentile
Published
2026-07-21T12:37Z
EPSS history
Timeline
  • 21 JUL 12:37Z
    Site isolation issue in the Networking: HTTP component
    cvelistv5