CVE-2020-26960: Mozilla Firefox

High severity, CVSS 8.8. EPSS: 1.6% chance of exploitation in the next 30 days.

If the Compact() method was called on an nsTArray, the array could have been reallocated without updating other pointers, leading to a potential use-after-free and exploitable crash. This vulnerability affects Firefox < 83, Firefox ESR < 78.5, and Thunderbird < 78.5.

Affected products

• Mozilla Firefox: before 83.0 (fixed in 83.0)
• Mozilla Firefox ESR: before 78.5 (fixed in 78.5)
• Mozilla Thunderbird: before 78.5 (fixed in 78.5)

Published 2020-12-09. Last modified 2026-06-17.