CVE-2021-23973: Debian Linux

Medium severity, CVSS 6.5. EPSS: 1.4% chance of exploitation in the next 30 days.

When trying to load a cross-origin resource in an audio/video context a decoding error may have resulted, and the content of that error may have revealed information about the resource. 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.