High-severity RCE-capable use-after-free in widely used Mozilla Firefox (ESR) and Thunderbird clients; enterprise ESR usage makes it broadly important to IT teams.
CVE-2026-100832
Use-after-free in Canvas2D enabling remote code execution in Firefox/Thunderbird
Is CVE-2026-100832 being exploited?
Not confirmed. CVE-2026-100832 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-2026-100832?
CVE-2026-100832 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-2026-100832?
Yes. A fix has been recorded for CVE-2026-100832. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-100832 affect?
CVE-2026-100832 affects Mozilla Firefox (ESR and release; fixed in ESR 153.4, 140.17, 115.42), Mozilla Thunderbird (fixed in 140.17 and 153.4). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-100832?
Apply Mozilla security updates immediately to the fixed versions listed in advisory.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Memory corruption (use-after-free) in Canvas2D can be triggered by crafted web/email content, enabling remote code execution or crashes.
Immediate action required