Affects Firefox/Thunderbird; high-severity browser policy bypass with cross-origin exposure risk.
CVE-2026-8948
Same-origin policy bypass in browser DOM networking.
Is CVE-2026-8948 being exploited?
Not confirmed. CVE-2026-8948 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 0.42% probability of exploitation in the next 30 days.
How severe is CVE-2026-8948?
CVE-2026-8948 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-2026-8948?
Yes. A fix has been recorded for CVE-2026-8948. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-8948 affect?
CVE-2026-8948 affects Firefox, Thunderbird. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-8948?
Update to patched Firefox/Thunderbird 151+
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Bypass of same-origin policy enabling cross-origin data access/exfiltration via the browser's networking component.
Patch when possible