CVE-2026-84124

CVE-2026-84124

Use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 155, Firefox ESR 140.15, Firefox ESR 153.2, Thunderbird 155, Thunderbird 140.15, and Thunderbird 153.2.

Vulnerability class: Use-After-Free

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N.

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-84124?
CVE-2026-84124 is a medium-severity vulnerability, classified under Use After Free. CVSS score: 5.4/10. Published 2026-09-01.
How severe is CVE-2026-84124?
Medium severity. CVSS v3 base score is 5.4 out of 10.