What is CVE-2026-16378?

CVE-2026-16378 is a high-severity vulnerability in Mozilla Firefox, classified under Improper Input Validation. CVSS score: 7.5/10. Published 2026-07-21.

How severe is CVE-2026-16378?

High severity. CVSS v3 base score is 7.5 out of 10.

Improper input validation in Mozilla Firefox

CVE-2026-16378

Other issue in the DOM: Copy & Paste and Drag & Drop component. This vulnerability was fixed in Firefox 153 and Thunderbird 153.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

EPSS: 0.003 (22.9th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.

Affected products

Mozilla Firefox — versions 153
Mozilla Thunderbird — versions 153

Weakness classification (CWE)

CWE-20 — Improper Input Validation

References

security@mozilla.org (Permissions Required)
security@mozilla.org (Vendor Advisory)
security@mozilla.org (Vendor Advisory)

Frequently asked questions

What is CVE-2026-16378?: CVE-2026-16378 is a high-severity vulnerability in Mozilla Firefox, classified under Improper Input Validation. CVSS score: 7.5/10. Published 2026-07-21.
How severe is CVE-2026-16378?: High severity. CVSS v3 base score is 7.5 out of 10.