CVE-2026-84143
Critical
9.8 CVSS v3.1
- Published
- Sep 1, 2026
- Updated
- Sep 3, 2026
- Vendor
- Mozilla
- Affected versions
- See affected products
- Weakness
- CWE-119, CWE-200
Summary
Internally found bugs present in Thunderbird 154, Thunderbird ESR 153.1 and Thunderbird 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. This vulnerability was fixed in Firefox 155, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.
Severity
Critical (9.8)CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Affected products
- Mozilla Firefox < 140.15.0
- Mozilla Firefox >= 141.0.0, < 153.2.0
- Mozilla Firefox >= 154.0.0, < 155.0.0
- Mozilla Thunderbird < 140.15.0
- Mozilla Thunderbird >= 141.0, < 153.2.0
- Mozilla Thunderbird >= 154.0, < 155.0
Exploitation status
Unknown
Technical details
Technical analysis has not been written for this record yet.
Mitigation & remediation
Follow the vendor advisory linked below for patches and workarounds.