Mozilla · Thunderbird · CVE-2026-84120
**Name of the Vulnerable Software and Affected Versions**
Firefox versions prior to 155
Firefox ESR versions prior to 115.40
Firefox ESR versions prior to 140.15
Firefox ESR versions prior to 153.2
Thunderbird versions prior to 155
Thunderbird versions prior to 140.15
Thunderbird versions prior to 153.2
**Description**
A use-after-free issue exists in the Audio/Video 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.
Update Firefox ESR to version 115.40.
Update Firefox ESR to version 140.15.
Update Firefox ESR to version 153.2.
Update Thunderbird to version 155.
Update Thunderbird to version 140.15.
Update Thunderbird to version 153.2.