CVE-2026-84121: Sandbox escape due to use-after-free in the DOM: Security component
Sandbox escape due to use-after-free in the DOM: Security component. This vulnerability was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, and Firefox ESR 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 140.15 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 115.40 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 153.2 - Upgrade
Upgrade
Firefoxto a version that resolves this vulnerability.Fixed in 155 - Upgrade
Upgrade
Firefox ESRto a version that resolves this vulnerability.Fixed in 115.40 - Upgrade
Upgrade
Firefox ESRto a version that resolves this vulnerability.Fixed in 140.15 - Upgrade
Upgrade
Firefox ESRto 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-2026-16365
- CVE-2026-16371
- CVE-2026-74952
Frequently Asked Questions
Which Firefox releases contain the fix?
The issue was fixed in Firefox 155, Firefox ESR 115.40, Firefox ESR 140.15, and Firefox ESR 153.2.
What type of weakness underlies this issue?
It is a use-after-free vulnerability in the DOM security component that can lead to a sandbox escape.