CVE-2026-84126: Incorrect boundary conditions in the Layout: Grid component
Incorrect boundary conditions in the Layout: Grid component. This vulnerability was fixed in Firefox 155 and Thunderbird 155.
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
Mozilla Firefoxto a version that resolves this vulnerability.Fixed in 155 - Upgrade
Upgrade
Mozilla Thunderbirdto a version that resolves this vulnerability.Fixed in 155
Event History
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-2026-84639
- CVE-2026-84640
- CVE-2026-84641
- CVE-2026-84642
Frequently Asked Questions
Which Firefox versions need to be updated?
The issue was fixed in Firefox 155. The provided information does not identify the first affected version or whether any specific release channels are excluded.
What exploitation conditions or temporary mitigations are documented?
The provided information does not describe attacker prerequisites, affected default settings, indicators of compromise, or a workaround for systems that cannot yet update. Updating to Firefox 155 is the documented remediation.