An out-of-bounds read vulnerability with the Opus encoder when the number of channels in an audio stream changes while the encoder is in use. This vulnerability affects Firefox < 54, Firefox ESR < 52.2, and Thunderbird < 52.2.
Severity
CVSS 3.0
9.1 critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
EPSS
3.0% chance of exploitation in the next 30 days; higher than 87% of CVEs (scores of 2026-10-31)