CVE-2020-6806: Canonical Ubuntu Linux

High severity, CVSS 8.8. EPSS: 2.6% chance of exploitation in the next 30 days.

By carefully crafting promise resolutions, it was possible to cause an out-of-bounds read off the end of an array resized during script execution. This could have led to memory corruption and a potentially exploitable crash. This vulnerability affects Thunderbird < 68.6, Firefox < 74, Firefox < ESR68.6, and Firefox ESR < 68.6.

Affected products

• Canonical Ubuntu Linux: version 16.04 only; version 18.04 only; version 19.10 only
• Mozilla Firefox: before 74.0 (fixed in 74.0)
• Mozilla Firefox ESR: before 68.6.0 (fixed in 68.6.0)
• Mozilla Thunderbird: before 68.6.0 (fixed in 68.6.0)

Published 2020-03-25. Last modified 2026-06-17.