CVE-2026-74942
Privilege escalation in Firefox/Thunderbird Remote Settings Client
Is CVE-2026-74942 being exploited?
Not confirmed. CVE-2026-74942 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 0.30% probability of exploitation in the next 30 days.
How severe is CVE-2026-74942?
CVE-2026-74942 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-2026-74942?
Yes. A fix has been recorded for CVE-2026-74942. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-74942 affect?
CVE-2026-74942 affects Mozilla Firefox (pre-154), Firefox ESR (versions before 115.39 / 140.14 / 153.1), Mozilla Thunderbird (pre-154 and affected ESRs). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-74942?
Update Firefox and Thunderbird to the listed fixed versions immediately
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Local privilege escalation allowing an attacker to elevate OS privileges and execute actions as a higher-privileged user.
Patch when possible