A use-after-free vulnerability can occur after deleting a selection element due to a weak reference to the select element in the options collection. This results in a potentially exploitable crash. This vulnerability affects Thunderbird < 60.4, Firefox ESR < 60.4, and Firefox < 64.
Severity
CVSS 3.0
9.8 critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
9.6% chance of exploitation in the next 30 days; higher than 95% of CVEs (scores of 2026-10-31)