CVE-2026-84140

Site isolation issue in the DOM: Navigation component

State: Published
Severity: 9.8 Critical
Published: Sep 1, 2026
Updated: Sep 3, 2026
Reserved: Sep 1, 2026

Description

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.

Scores

CVSS	Score	Vector	Source
3.1	9.8 Critical	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H	CISA-ADP

Weaknesses

CWE-346 Origin Validation Error

Affected Products

Product	Versions
FirefoxMozilla	153.2 through 153.*Not affected 155 and laterNot affected
ThunderbirdMozilla	153.2 through 153.*Not affected 155 and laterNot affected

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2063780
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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