Memory-corruption in widely used Firefox/Thunderbird enabling potential remote code execution; affects many users and warrants broad IT notification.
CVE-2026-100756
Memory-corruption in AV playback in Firefox/Thunderbird enabling remote code execution.
Is CVE-2026-100756 being exploited?
Not confirmed. CVE-2026-100756 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.
How severe is CVE-2026-100756?
CVE-2026-100756 is rated High with a CVSS score of 8.1. 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-2026-100756?
Yes. A fix has been recorded for CVE-2026-100756. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-100756 affect?
CVE-2026-100756 affects Mozilla Firefox, Firefox ESR, Mozilla Thunderbird. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-100756?
Upgrade Firefox/Thunderbird to the listed fixed versions immediately.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Memory corruption in audio/video playback allowing remote code execution or denial-of-service via crafted media.
Immediate action required