What is CVE-2026-16398?

CVE-2026-16398 is a high-severity vulnerability in Mozilla Firefox, classified under Information Disclosure. CVSS score: 7.5/10. Published 2026-07-21.

How severe is CVE-2026-16398?

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

Information disclosure in Mozilla Firefox

CVE-2026-16398

Site isolation issue in the Graphics component. This vulnerability was fixed in Firefox 153 and Thunderbird 153.

Vulnerability class: Information Disclosure

EPSS: 0.001 (4.4th 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-200 — Information Disclosure
CWE-346 — Origin Validation Error

References

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

Frequently asked questions

What is CVE-2026-16398?: CVE-2026-16398 is a high-severity vulnerability in Mozilla Firefox, classified under Information Disclosure. CVSS score: 7.5/10. Published 2026-07-21.
How severe is CVE-2026-16398?: High severity. CVSS v3 base score is 7.5 out of 10.