CVE-2020-12395: Canonical Ubuntu Linux

Critical severity, CVSS 9.8. EPSS: 2.5% chance of exploitation in the next 30 days.

Mozilla developers and community members reported memory safety bugs present in Firefox 75 and Firefox ESR 68.7. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox ESR < 68.8, Firefox < 76, and Thunderbird < 68.8.0.

Affected products

• Canonical Ubuntu Linux: version 16.04 only; version 18.04 only; version 19.10 only; version 20.04 only
• Mozilla Firefox: before 76.0 (fixed in 76.0)
• Mozilla Firefox ESR: before 68.8.0 (fixed in 68.8.0)
• Mozilla Thunderbird: before 68.8.0 (fixed in 68.8.0)

Published 2020-05-26. Last modified 2026-06-17.