CVE-2021-23982: Mozilla Firefox

Medium severity, CVSS 6.5. EPSS: 0.7% chance of exploitation in the next 30 days.

Using techniques that built on the slipstream research, a malicious webpage could have scanned both an internal network's hosts as well as services running on the user's local machine utilizing WebRTC connections. This vulnerability affects Firefox ESR < 78.9, Firefox < 87, and Thunderbird < 78.9.

Affected products

• Mozilla Firefox: before 87.0 (fixed in 87.0)
• Mozilla Firefox ESR: before 78.9 (fixed in 78.9)
• Mozilla Thunderbird: before 78.9 (fixed in 78.9)

Published 2021-03-31. Last modified 2026-06-17.