by Kastro
Paper/Archive/CVE-2026-16387

CVE-2026-16387

Mozilla Firefox — Site isolation issue in the Networking component

EPSS 0.3%CVSS 9.8
critical.is priorityof 100
34
CVSS 9.8 (ADP)9.8 / 10 × 3029.4Not in CISA KEV+300.0EPSS percentile 21.0.210 × 204.2No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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

Affected

ProductAffectedFixed inSource
Firefoxsee advisory140.13CNA
Thunderbirdsee advisory140.13CNA

Scores by source

CISA ADP9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CISA ADPSSVCExploitation: none · Automatable: yes · Technical impact: total

References

refbugzilla.mozilla.org/show_bug.cgi?id=2043200refmozilla.org/security/advisories/mfsa2026-68refmozilla.org/security/advisories/mfsa2026-70refmozilla.org/security/advisories/mfsa2026-71refmozilla.org/security/advisories/mfsa2026-72