CVE-2026-84142
Internally found bugs fixed in Thunderbird 155
CVSS Score
9.8
EPSS Score
0.0%
EPSS Percentile
0th
Internally found bugs present in Thunderbird 154. 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 and Thunderbird 155.
| Vendor | mozilla |
| Product | firefox |
| Ecosystems | |
| Industries | Technology |
| Published | Sep 1, 2026 |
| Last Updated | Sep 3, 2026 |
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Affected Versions
Mozilla / Firefox
All versions affected Mozilla / Thunderbird
All versions affected References
bugzilla.mozilla.org: https://bugzilla.mozilla.org/buglist.cgi?bug_id=2029421%2C2040889%2C2045313%2C2045435%2C2053578%2C2058621%2C2058626 bugzilla.mozilla.org: https://bugzilla.mozilla.org/buglist.cgi?bug_id=2048796%2C2053150%2C2057356 mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-82/ mozilla.org: https://www.mozilla.org/security/advisories/mfsa2026-86/
Credits
Alexandre Poirot, Christian Holler, Sebastian Hengst and the Mozilla Fuzzing Team