Critical severity · published Sep 1, 2026
CVE-2026-84119
Sandbox escape due to use-after-free in the DOM: Navigation component
9.6
CVSS
0.3%
EPSS
No
On KEV
Description
Sandbox escape due to use-after-free in the DOM: Navigation component. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
High
Integrity
High
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 25% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FI
Firefox · Mozilla
before 115.40.0; 116.0 before 140.15.0; 141.0.0 before 153.2.0; 154.0.0 before 155.0.0 · source: NVD
TH
Thunderbird · Mozilla
before 140.15.0; 141.0 before 153.2.0; 154.0 before 155.0 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-84119
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-84119
Permissions Required
https://bugzilla.mozilla.org/show_bug.cgi?id=2057817
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-82/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-83/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-84/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-85/
Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-86/
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