CVE-2020-26977: Mozilla Firefox Mobile

Medium severity, CVSS 6.5. EPSS: 0.9% chance of exploitation in the next 30 days.

By attempting to connect a website using an unresponsive port, an attacker could have controlled the content of a tab while the URL bar displayed the original domain. *Note: This issue only affects Firefox for Android. Other operating systems are unaffected.*. This vulnerability affects Firefox < 84.

Affected products

• Mozilla Firefox Mobile: before 84.0 (fixed in 84.0)

Published 2021-01-07. Last modified 2026-08-19.