CVE-2026-84143: Internally found bugs fixed in Firefox 155, Firefox ESR 153.2 and Firefox ESR 140.15
Internally found bugs present in Firefox 154, Firefox ESR 153.1 and Firefox ESR 140.14. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited.
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 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 153.2 - Upgrade
Upgrade
Firefox ESRto a version that resolves this vulnerability.Fixed in 140.15
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 need to be updated?
Affected releases are Firefox 154, Firefox ESR 153.1, and Firefox ESR 140.14. The fixes are available in Firefox 155, Firefox ESR 153.2, and Firefox ESR 140.15.
Is exploitation confirmed?
No exploitation is confirmed in the provided information. Mozilla reported that some of the internally found bugs showed evidence of memory corruption or another security-relevant defect and could potentially be exploitable with enough effort.