CVE-2026-74987
Memory-corruption in Thunderbird/Firefox 153 allowing remote code execution.
Is CVE-2026-74987 being exploited?
Not confirmed. CVE-2026-74987 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 0.52% probability of exploitation in the next 30 days.
How severe is CVE-2026-74987?
CVE-2026-74987 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-2026-74987?
Yes. A fix has been recorded for CVE-2026-74987. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-74987 affect?
CVE-2026-74987 affects Mozilla Thunderbird 153, Thunderbird ESR 140.13, Thunderbird ESR 153.0, Mozilla Firefox 153 (shared code). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-74987?
Immediately update to Thunderbird 154/ESR 140.14 or 153.1 and Firefox 154.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Memory corruption can be triggered by crafted content/messages leading to remote arbitrary code execution and full client compromise.
Immediate action required