CVE-2026-84142Internally found bugs fixed in Thunderbird 155
Updated under an hour ago ()
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It affects Mozilla Firefox and 1 other product. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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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.
- 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) | from 155 not affected | CNA record |
Mozilla Thunderbird mozilla:thunderbird (from the name) | from 155 not affected | CNA record |
mozilla firefox mozilla:firefox | before 155.0.0 | NVD |
mozilla thunderbird mozilla:thunderbird | before 155.0 | NVD |
References
- https://bugzilla.mozilla.org/buglist.cgi?bug_id=2029421%2C2040889%2C2045313%2C2045435%2C2053578%2C2058621%2C2058626issue-tracking
- https://bugzilla.mozilla.org/buglist.cgi?bug_id=2048796%2C2053150%2C2057356issue-tracking
- https://www.mozilla.org/security/advisories/mfsa2026-82/vendor-advisory
- https://www.mozilla.org/security/advisories/mfsa2026-86/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.