CVE-2026-84143Internally found bugs fixed in Thunderbird 155, Thunderbird ESR 153.2 and Thunderbird ESR 140.15
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 9.8 CRITICAL (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- CWE-200
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- mozilla
- NVD analysis
- Modified
- Record last updated
- Sep 3, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Mozilla Firefox mozilla:firefox (from the name) | 140.15 builds before 140.* not affected; 153.2 builds before 153.* not affected; from 155 not affected | CNA record |
Mozilla Thunderbird mozilla:thunderbird (from the name) | 140.15 builds before 140.* not affected; 153.2 builds before 153.* not affected; from 155 not affected | CNA record |
mozilla firefox mozilla:firefox | before 140.15.0; from 141.0.0 before 153.2.0; from 154.0.0 before 155.0.0 | NVD |
mozilla thunderbird mozilla:thunderbird | before 140.15.0; from 141.0 before 153.2.0; from 154.0 before 155.0 | NVD |
References
- https://bugzilla.mozilla.org/buglist.cgi?bug_id=2048793%2C2054645%2C2057114%2C2059109%2C2061287issue-tracking
- https://bugzilla.mozilla.org/buglist.cgi?bug_id=2054631%2C2054657%2C2055007%2C2055681%2C2057107%2C2058087%2C2058088%2C2058090%2C2058095%2C2058101%2C2059183%2C2059185%2C2061301%2C2061325issue-tracking
- https://bugzilla.mozilla.org/show_bug.cgi?id=2057108issue-tracking
- https://www.mozilla.org/security/advisories/mfsa2026-82/vendor-advisory
- https://www.mozilla.org/security/advisories/mfsa2026-84/vendor-advisory
- https://www.mozilla.org/security/advisories/mfsa2026-85/vendor-advisory
- https://www.mozilla.org/security/advisories/mfsa2026-86/vendor-advisory
- https://www.mozilla.org/security/advisories/mfsa2026-87/vendor-advisory
- https://www.mozilla.org/security/advisories/mfsa2026-88/vendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.