What is CVE-2026-2803?

CVE-2026-2803 is a high-severity vulnerability in Mozilla Firefox, classified under Information Disclosure. CVSS score: 7.5/10. Published 2026-02-24.

How severe is CVE-2026-2803?

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

Information disclosure in Mozilla Firefox

CVE-2026-2803

Information disclosure, mitigation bypass in the Settings UI component. This vulnerability was fixed in Firefox 148 and Thunderbird 148.

Vulnerability class: Information Disclosure

Published 2026-02-24 · last modified 2026-06-17.

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.

EPSS exploit prediction

EPSS: 0.004 (36.2th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 36th percentile — 36.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.004 · change: +0.002

Affected products

Mozilla Firefox — versions 148
Mozilla Thunderbird — versions 148

Weakness classification (CWE)

References

bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
www.mozilla.org/security/advisories/mfsa2026-13/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2026-16/ (Vendor Advisory)

Frequently asked questions

What is CVE-2026-2803?: CVE-2026-2803 is a high-severity vulnerability in Mozilla Firefox, classified under Information Disclosure. CVSS score: 7.5/10. Published 2026-02-24.
How severe is CVE-2026-2803?: High severity. CVSS v3 base score is 7.5 out of 10.