CVE-2026-84140: Site isolation issue in the DOM: Navigation component
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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 155 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 153.2 - Upgrade
Upgrade
Mozilla Firefox / Firefox ESR / Thunderbirdto a version that resolves this vulnerability.Fixed in 155 - Upgrade
Upgrade
Mozilla Firefox ESR / Thunderbird 153.2to a version that resolves this vulnerability.Fixed in 153.2
Event History
Parent advisories
This vulnerability appears in the following advisories.
Peer vulnerabilities
Found alongside the following vulnerabilities.
- CVE-2026-84117
- CVE-2026-84118
- CVE-2026-84119
- CVE-2026-84120
- CVE-2026-84121
- CVE-2026-84122
- CVE-2026-84123
- CVE-2026-84124
- CVE-2026-84125
- CVE-2026-84126
- CVE-2026-84127
- CVE-2026-84128
- CVE-2026-84129
- CVE-2026-84130
- CVE-2026-84131
- CVE-2026-84132
- CVE-2026-84133
- CVE-2026-84134
- CVE-2026-84135
- CVE-2026-84136
- CVE-2026-84137
- CVE-2026-84138
- CVE-2026-84139
- CVE-2026-84140
- CVE-2026-84141
- CVE-2026-84142
- CVE-2026-84143
- CVE-2026-84144
- CVE-2026-84145
- CVE-2026-75874
- CVE-2026-74952
- CVE-2026-84639
- CVE-2026-84640
- CVE-2026-84641
- CVE-2026-84642
- CVE-2026-84637
Frequently Asked Questions
Which Firefox releases contain the fix?
The issue was fixed in Firefox 155 and Firefox ESR 153.2.
Which products should be checked for exposure?
Mozilla Firefox and Mozilla Firefox ESR should be checked. Installations not yet updated to Firefox 155 or Firefox ESR 153.2 may not include the fix.