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Vulnerability record · CVE-2026-84145 · published 1 September 2026

CVE-2026-84145: Mozilla firefox memory buffer overflow vulnerability

Mozilla · Firefox

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 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.

7.5 CVSS 3.1 High EPSS 0.37% · top 71.7% CWE-119 · Memory buffer overflow
7.5CVSS 3.1 base score
0.37%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
10References
3 Sep 2026Last modified by NVD

Description

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 115.40, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://bugzilla.mozilla.org/buglist.cgi?bug_id=2054640%2C2054650%2C2054652%2C2055693%2C2055705%2C2058051%2C2058652%2C20 Broken Link
https://bugzilla.mozilla.org/buglist.cgi?bug_id=2058001%2C2059139%2C2062400%2C2062419 Broken Link
https://bugzilla.mozilla.org/show_bug.cgi?id=2055678 Permissions Required
https://www.mozilla.org/security/advisories/mfsa2026-82/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2026-83/ 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

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-84145), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.