CVE-2026-74990
firefox: thunderbird: Internally found bugs fixed in Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1 and Firefox 154
Severity
ImportantRed Hat Product Security
CVSS 3.1
Review impact separately from score.
Published · August 18, 2026
Updated · September 9, 2026
Description
A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue: Internally found bugs present in Thunderbird ESR 140.13, Thunderbird ESR 153.0 and Thunderbird 153. 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.
Statement
Red Hat Product Security rates the severity of this flaw as determined by the Mozilla Foundation Security Advisory.
CVSS score applicability
The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.
Mitigation
No mitigation is specified in collected source.
CVSS / CWE
CVSS 3.1 · 7.5CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
CWE-787 · Out-of-bounds Write