CVE-2026-5735
Memory safety bugs in Firefox/Thunderbird may allow remote code execution.
Is CVE-2026-5735 being exploited?
Not confirmed. CVE-2026-5735 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 0.26% probability of exploitation in the next 30 days.
How severe is CVE-2026-5735?
CVE-2026-5735 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-2026-5735?
Yes. A fix has been recorded for CVE-2026-5735. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-5735 affect?
CVE-2026-5735 affects Firefox < 149.0.2, Thunderbird < 149.0.2. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-5735?
Patch to 149.0.2 or later
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Potential remote code execution via memory corruption in Firefox/Thunderbird prior to 149.0.2.
Immediate action required