What is CVE-2026-12303?

CVE-2026-12303 is a medium-severity vulnerability in Mozilla Firefox, classified under Out-of-bounds Read. CVSS score: 4.3/10. Published 2026-06-16.

How severe is CVE-2026-12303?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Out-of-bounds Read in Mozilla Firefox

CVE-2026-12303

Information disclosure due to incorrect boundary conditions in the Graphics: WebGPU component. This vulnerability was fixed in Firefox 152 and Thunderbird 152.

Vulnerability class: Buffer Overflow

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N.

Affected products

Mozilla Firefox — versions 152
Mozilla Thunderbird — versions 152

Weakness classification (CWE)

CWE-125 — Out-of-bounds Read

References

security@mozilla.org
security@mozilla.org
security@mozilla.org

Frequently asked questions

What is CVE-2026-12303?: CVE-2026-12303 is a medium-severity vulnerability in Mozilla Firefox, classified under Out-of-bounds Read. CVSS score: 4.3/10. Published 2026-06-16.
How severe is CVE-2026-12303?: Medium severity. CVSS v3 base score is 4.3 out of 10.