Internally found bugs present in 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. This vulnerability was fixed in Firefox 154 and Thunderbird 154.

A flaw was found in Firefox. The Mozilla Foundation's Security Advisory describes the following issue: Internally found bugs present in Firefox 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.

Red Hat Product Security rates the severity of this flaw as determined by the Mozilla Foundation Security Advisory. Red Hat Enterprise Linux 10 Not affected firefox Red Hat Enterprise Linux 10 Not affected rhel10/firefox-flatpak Red Hat Enterprise Linux 10 Not affected rhel10/thunderbird-flatpak Red Hat Enterprise Linux 10 Not affected thunderbird Red Hat Enterprise Linux 6 Not affected firefox Red Hat Enterprise Linux 6 Not affected thunderbird Red Hat Enterprise Linux 7 Not affected firefox Red Hat Enterprise Linux 7 Not affected thunderbird Red Hat Enterprise Linux 8 Not affected firefox Red Hat Enterprise Linux 8 Not affected thunderbird Red Hat Enterprise Linux 9 Not affected firefox Red Hat Enterprise Linux 9 Not affected thunderbird https://www.cve.org/CVERecord?id=CVE-2026-74989 https://nvd.nist.gov/vuln/detail/CVE-2026-74989 https://www.mozilla.org/security/advisories/mfsa2026-74/#CVE-2026-74989 https://www.mozilla.org/security/advisories/mfsa2026-78/#CVE-2026-74989