CVE-2026-2787
Use-after-free in DOM Window/Location may lead to RCE in Firefox/Thunderbird.
Is CVE-2026-2787 being exploited?
Not confirmed. CVE-2026-2787 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 0.40% probability of exploitation in the next 30 days.
How severe is CVE-2026-2787?
CVE-2026-2787 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-2026-2787?
Yes. A fix has been recorded for CVE-2026-2787. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-2787 affect?
CVE-2026-2787 affects Firefox < 148, Firefox ESR < 115.33, Firefox ESR < 140.8, Thunderbird < 148, and 1 further product or version. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-2787?
Update to latest Firefox/Thunderbird.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
RCE via crafted web content exploiting DOM use-after-free in affected browsers.
Immediate action required