CVE-2020-12405: Canonical Ubuntu Linux

Medium severity, CVSS 5.3. EPSS: 1.4% chance of exploitation in the next 30 days.

When browsing a malicious page, a race condition in our SharedWorkerService could occur and lead to a potentially exploitable crash. This vulnerability affects Thunderbird < 68.9.0, Firefox < 77, and Firefox ESR < 68.9.

Affected products

• Canonical Ubuntu Linux: version 16.04 only; version 18.04 only; version 19.10 only; version 20.04 only
• Mozilla Firefox: before 77.0 (fixed in 77.0)
• Mozilla Firefox ESR: before 68.9.0 (fixed in 68.9.0)
• Mozilla Thunderbird: before 68.9.0 (fixed in 68.9.0)

Published 2020-07-09. Last modified 2026-06-17.