CVE-2026-74981
Site isolation bypass in WebCodecs allowing cross-origin media data exposure
Is CVE-2026-74981 being exploited?
Not confirmed. CVE-2026-74981 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 0.15% probability of exploitation in the next 30 days.
How severe is CVE-2026-74981?
CVE-2026-74981 is rated High with a CVSS score of 8.1. 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-2026-74981?
Yes. A fix has been recorded for CVE-2026-74981. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-74981 affect?
CVE-2026-74981 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-2026-74981?
Upgrade to Firefox 154 / ESR 153.1 and Thunderbird 154+ immediately; deploy via patch management
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Bypass of site isolation in WebCodecs enables cross-origin access to media buffers, causing information disclosure of other sites' content.
Immediate action required