CVE-2026-16387

critical

Description

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

References

https://www.mozilla.org/security/advisories/mfsa2026-72/

https://www.mozilla.org/security/advisories/mfsa2026-71/

https://www.mozilla.org/security/advisories/mfsa2026-70/

https://www.mozilla.org/security/advisories/mfsa2026-68/

https://bugzilla.mozilla.org/show_bug.cgi?id=2043200

Details

Source: Mitre, NVD

Published: 2026-07-21

Updated: 2026-07-22

Risk Information

CVSS v2

Base Score: 10

Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:C

Severity: Critical

CVSS v3

Base Score: 9.8

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H