CVE-2019-11757: Canonical Ubuntu Linux

High severity, CVSS 8.8. EPSS: 1.4% chance of exploitation in the next 30 days.

When following the value's prototype chain, it was possible to retain a reference to a locale, delete it, and subsequently reference it. This resulted in a use-after-free and a potentially exploitable crash. This vulnerability affects Firefox < 70, Thunderbird < 68.2, and Firefox ESR < 68.2.

Affected products

• Canonical Ubuntu Linux: version 16.04 only
• Mozilla Firefox: before 70.0 (fixed in 70.0)
• Mozilla Firefox ESR: before 68.2 (fixed in 68.2)
• Mozilla Thunderbird: before 68.2 (fixed in 68.2)

Published 2020-01-08. Last modified 2026-06-17.