by Kastro
Paper/Archive/CVE-2026-84140

CVE-2026-84140

Mozilla Firefox — Site isolation issue in the DOM: Navigation component

EPSS 0.2%CVSS 9.8
critical.is priorityof 100
31
CVSS 9.8 (ADP, NVD agree)9.8 / 10 × 3029.4Not in CISA KEV+300.0EPSS percentile 7.8.078 × 201.6No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

Site isolation issue in the DOM: Navigation component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.

Affected

ProductAffectedFixed inSource
Firefoxsee advisory153.2CNA
Thunderbirdsee advisory153.2CNA

Scores by source

CISA ADP9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD9.8CVSS: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=2063780refmozilla.org/security/advisories/mfsa2026-82refmozilla.org/security/advisories/mfsa2026-85refmozilla.org/security/advisories/mfsa2026-86refmozilla.org/security/advisories/mfsa2026-88