CVE-2026-74983
DLP mitigation bypass in Firefox/Thunderbird enabling sensitive data leaks.
Is CVE-2026-74983 being exploited?
Not confirmed. CVE-2026-74983 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 0.33% probability of exploitation in the next 30 days.
How severe is CVE-2026-74983?
CVE-2026-74983 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-2026-74983?
Yes. A fix has been recorded for CVE-2026-74983. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-74983 affect?
CVE-2026-74983 affects Mozilla Firefox (desktop) prior to 154, Firefox ESR prior to 140.14 and 153.1, Mozilla Thunderbird prior to 154 (and ESR 140.14/153.1). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-74983?
Upgrade Firefox and Thunderbird to the specified fixed versions immediately.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Bypasses Data Loss Prevention controls, allowing disclosure or exfiltration of sensitive data via web/email content handling.
Immediate action required