CVE-2026-84124

Name of the Vulnerable Software and Affected Versions Firefox versions prior to 155 Firefox ESR versions prior to 140.15 Firefox ESR versions prior to 153.2 Thunderbird versions prior to 155 Thunderbird ESR versions prior to 140.15 Thunderbird ESR versions prior to 153.2

Description A use-after-free issue exists within the DOM: Core & HTML component. Use-after-free is a memory corruption flaw that occurs when an application continues to use a pointer after it has been freed, which can lead to crashes or arbitrary code execution.

Recommendations Update Firefox to version 155 or later. Update Firefox ESR to version 140.15 or later. Update Firefox ESR to version 153.2 or later. Update Thunderbird to version 155 or later. Update Thunderbird ESR to version 140.15 or later. Update Thunderbird ESR to version 153.2 or later.