CVE-2026-84129

CRITICAL 9.8

Site isolation issue in the DOM: Navigation component

CVSS Score

9.8

EPSS Score

0.0%

EPSS Percentile

0th

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.

Vendor	mozilla
Product	firefox
Ecosystems	Browser JavaScript
Industries	Technology
Published	Sep 1, 2026
Last Updated	Sep 2, 2026

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Affected Versions

Mozilla / Firefox

All versions affected

Mozilla / Thunderbird

All versions affected

References

NVD ↗ CVE.org ↗ EPSS Data ↗

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

Credits

Yaqoub Aldurayhim