Widely used Firefox/Thunderbird; potential RCE via Canvas2D, high disruption risk.
CVE-2026-4725
Canvas2D use-after-free sandbox escape in Firefox <149 and Thunderbird <149.
Is CVE-2026-4725 being exploited?
Not confirmed. CVE-2026-4725 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 0.32% probability of exploitation in the next 30 days.
How severe is CVE-2026-4725?
CVE-2026-4725 is rated Critical with a CVSS score of 10.0. 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-2026-4725?
Yes. A fix has been recorded for CVE-2026-4725. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-4725 affect?
CVE-2026-4725 affects Firefox < 149, Thunderbird < 149. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-4725?
Upgrade to Firefox 149+ and Thunderbird 149+ immediately
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Sandbox escape could allow remote code execution from a crafted page/mail, breaking containment.
Immediate action required