Affects widely-used Mozilla Firefox/Thunderbird; critical RCE risk via JS GC use-after-free; potential org-wide impact.
CVE-2026-2797
Use-after-free in Firefox/Thunderbird JS GC; RCE risk on <148
Is CVE-2026-2797 being exploited?
Not confirmed. CVE-2026-2797 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-2026-2797?
CVE-2026-2797 is rated Critical with a CVSS score of 9.8. 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-2026-2797?
Yes. A fix has been recorded for CVE-2026-2797. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-2797 affect?
CVE-2026-2797 affects Mozilla Firefox < 148, Mozilla Thunderbird < 148. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-2797?
Update to Firefox/Thunderbird >=148
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
RCE via crafted JavaScript in Firefox/Thunderbird; attacker could execute arbitrary code.
Patch when possible