CVE-2026-74943
Use-after-free in image handling enabling RCE via crafted image in Firefox/Thunderbird.
Is CVE-2026-74943 being exploited?
Not confirmed. CVE-2026-74943 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 0.57% probability of exploitation in the next 30 days.
How severe is CVE-2026-74943?
CVE-2026-74943 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-2026-74943?
Yes. A fix has been recorded for CVE-2026-74943. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-74943 affect?
CVE-2026-74943 affects Firefox 154 (fixed), Firefox ESR 115.39, 140.14, 153.1 (fixed), Thunderbird 154 (fixed), Thunderbird 140.14, 153.1 (fixed), 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-2026-74943?
Update Firefox/Thunderbird to the listed fixed releases immediately.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution or crash when a user processes a malicious image in the browser or email client.
Immediate action required