Mozilla · Firefox Esr · CVE-2026-4720
**Name of the Vulnerable Software and Affected Versions**
Firefox versions prior to 149
Firefox ESR versions prior to 140.9
Thunderbird versions prior to 149
Thunderbird ESR versions prior to 140.9
**Description**
The software contains memory safety bugs, some of which demonstrate evidence of memory corruption. It is presumed that, with sufficient effort, these bugs could potentially be exploited to execute arbitrary code.
**Recommendations**
Update Firefox to version 149 or later.
Update Firefox ESR to version 140.9 or later.
Update Thunderbird to version 149 or later.
Update Thunderbird ESR to version 140.9 or later.