What’s Vulnerable › Vulnerabilities

CVE-2021-23982

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-03-31 · updated 2026-06-17
• Weakness: CWE-326

Description

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

How to fix

Upgrade to a fixed version: Mozilla Firefox 87.0; Mozilla Firefox ESR 78.9; Mozilla Thunderbird 78.9. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1677046
• https://www.mozilla.org/security/advisories/mfsa2021-10/
• https://www.mozilla.org/security/advisories/mfsa2021-11/
• https://www.mozilla.org/security/advisories/mfsa2021-12/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1677046
• https://www.mozilla.org/security/advisories/mfsa2021-10/
• https://www.mozilla.org/security/advisories/mfsa2021-11/
• https://www.mozilla.org/security/advisories/mfsa2021-12/

Get alerted when CVE-2021-23982 or the next vulnerability affects your stack