Affects widely used Mozilla products (Firefox, Thunderbird); critical side-channel can enable cross-origin data leakage across organizations, warranting broad IT notification.
CVE-2026-74961
Critical Web Audio side-channel in Firefox/Thunderbird allowing sensitive data leakage.
Is CVE-2026-74961 being exploited?
Not confirmed. CVE-2026-74961 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.25% probability of exploitation in the next 30 days.
How severe is CVE-2026-74961?
CVE-2026-74961 is rated Critical with a CVSS score of 9.1. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-74961?
Yes. A fix has been recorded for CVE-2026-74961. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-74961 affect?
CVE-2026-74961 affects Mozilla Firefox < 154, Firefox ESR < 153.1, Mozilla Thunderbird < 154, Thunderbird ESR < 153.1. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-74961?
Update Firefox/Thunderbird to the fixed versions immediately.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote side-channel via Web Audio API enabling cross-origin data exfiltration (fingerprinting, secret/keystroke inference).
Immediate action required