Memory safety bugs were identified in Firefox 138, Thunderbird 138, Firefox ESR 128.10, and Thunderbird 128.10. These bugs showed evidence of memory corruption and could potentially be exploited to execute arbitrary code. The vulnerabilities have been fixed in Firefox 139, Thunderbird 139, Firefox ESR 128.11, and Thunderbird 128.11. The CVSS score for this issue is 6.5, indicating a medium severity level.