CVE-2026-84129: 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
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 installations need to be updated?
Mozilla Firefox installations earlier than version 155 and Mozilla Firefox ESR installations earlier than version 153.2 need to be updated.
How can administrators determine whether an installation is affected?
Check the installed Firefox version. Systems running Firefox 155 or later, or Firefox ESR 153.2 or later, include the fix.
What should be done if the browser cannot be updated immediately?
The provided information does not identify a configuration workaround or mitigation. Upgrade to a fixed Firefox or Firefox ESR release when possible.