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CVE-2026-84143Internally found bugs fixed in Thunderbird 155, Thunderbird ESR 153.2 and Thunderbird ESR 140.15
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.
9.8 CRITICALEPSS 0.37%Not in KEVNVD: Modified
Overview
Severity
| Score | Severity | Version | Vector String |
|---|---|---|---|
| 9.8 | CRITICAL | 3.1NVD | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
Details
- CVE ID
- CVE-2026-84143
- Status
- Modified
- Assigner (CNA)
- mozilla
- Published
- Sep 1, 2026
- Last modified
- 2026-09-03 18:17 UTC
Affected Products
As published by the CNA in the CVE record.
MozillaFirefox0 version ranges
No version detail published.
MozillaThunderbird0 version ranges
No version detail published.
References
- bugzilla.mozilla.org https://bugzilla.mozilla.org/buglist.cgi?bug_id=2048793%2C2054645%2C2057114%2C2059109%2C2061287
- bugzilla.mozilla.org https://bugzilla.mozilla.org/buglist.cgi?bug_id=2054631%2C2054657%2C2055007%2C2055681%2C2057107%2C2058087%2C2058088%2C2058090%2C2058095%2C2058101%2C2059183%2C2059185%2C2061301%2C2061325
- bugzilla.mozilla.org https://bugzilla.mozilla.org/show_bug.cgi?id=2057108
- mozilla.org https://www.mozilla.org/security/advisories/mfsa2026-82/
- mozilla.org https://www.mozilla.org/security/advisories/mfsa2026-84/
- mozilla.org https://www.mozilla.org/security/advisories/mfsa2026-85/
- mozilla.org https://www.mozilla.org/security/advisories/mfsa2026-86/
- mozilla.org https://www.mozilla.org/security/advisories/mfsa2026-87/
- mozilla.org https://www.mozilla.org/security/advisories/mfsa2026-88/