CVE-2019-9788: Mozilla Firefox

Critical severity, CVSS 9.8. EPSS: 2.2% chance of exploitation in the next 30 days.

Mozilla developers and community members reported memory safety bugs present in Firefox 65, Firefox ESR 60.5, and Thunderbird 60.5. Some of these bugs showed evidence of memory corruption and we presume that with enough effort that some of these could be exploited to run arbitrary code. This vulnerability affects Thunderbird < 60.6, Firefox ESR < 60.6, and Firefox < 66.

Affected products

• Mozilla Firefox: before 60.6.0 (fixed in 60.6.0); before 66.0 (fixed in 66.0)
• Mozilla Thunderbird: before 60.6.0 (fixed in 60.6.0)
• Red Hat Enterprise Linux: version 8.0 only
• Red Hat Enterprise Linux Eus: version 8.1 only; version 8.2 only; version 8.4 only
• Red Hat Enterprise Linux Server Aus: version 8.2 only; version 8.4 only
• Red Hat Enterprise Linux Server Tus: version 8.2 only; version 8.4 only

Published 2019-04-26. Last modified 2026-06-17.