CVE-2021-23968: Debian Linux

Medium severity, CVSS 4.3. EPSS: 1.3% chance of exploitation in the next 30 days.

If Content Security Policy blocked frame navigation, the full destination of a redirect served in the frame was reported in the violation report; as opposed to the original frame URI. This could be used to leak sensitive information contained in such URIs. This vulnerability affects Firefox < 86, Thunderbird < 78.8, and Firefox ESR < 78.8.

Affected products

• Debian Debian Linux: version 9.0 only; version 10.0 only
• Mozilla Firefox: before 86.0 (fixed in 86.0)
• Mozilla Firefox ESR: before 78.8 (fixed in 78.8)
• Mozilla Thunderbird: before 78.8 (fixed in 78.8)

Published 2021-02-26. Last modified 2026-06-17.