CVE-2026-84129

9.8 criticalEPSS 0.2%

Critical (9.8) in mozilla. EPSS 0.2% chance of exploitation in the next 30 days.

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.

Severity

CVSS 3.1

9.8 critical

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

EPSS: 0.2% chance of exploitation in the next 30 days; higher than 8% of CVEs (scores of 2026-10-31)
CWE: CWE-346
Published: 2026-09-01
Modified: 2026-09-03
Record from: the NVD, synced 2026-10-19

Affected

mozilla:firefox
mozilla:thunderbird

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2055028
https://www.mozilla.org/security/advisories/mfsa2026-82/
https://www.mozilla.org/security/advisories/mfsa2026-85/
https://www.mozilla.org/security/advisories/mfsa2026-86/
https://www.mozilla.org/security/advisories/mfsa2026-88/

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