CVE-2026-84123
Use-after-free in Firefox WebGPU enabling privilege escalation
Is CVE-2026-84123 being exploited?
Not confirmed. CVE-2026-84123 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 0.23% probability of exploitation in the next 30 days.
How severe is CVE-2026-84123?
CVE-2026-84123 is rated High with a CVSS score of 8.8. 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-2026-84123?
Yes. A fix has been recorded for CVE-2026-84123. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-84123 affect?
CVE-2026-84123 affects Firefox <155, Firefox ESR <153.2, Thunderbird <155, Thunderbird ESR <153.2. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-84123?
Update to Firefox 155 / ESR 153.2 and Thunderbird 155 / ESR 153.2
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
WebGPU use-after-free can enable sandbox escape and local privilege escalation, potentially allowing arbitrary code execution with user privileges.
Patch when possible