What is CVE-2026-12330?

CVE-2026-12330 is a medium-severity vulnerability in Mozilla Firefox, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 5.4/10. Published 2026-06-16.

How severe is CVE-2026-12330?

Medium severity. CVSS v3 base score is 5.4 out of 10.

Buffer overflow in Mozilla Firefox

CVE-2026-12330

Incorrect boundary conditions in the Internationalization component. This vulnerability was fixed in Firefox ESR 140.12, Firefox ESR 115.37, and Thunderbird 140.12.

Vulnerability class: Buffer Overflow

EPSS: 0.002 (6.1th percentile) — read the EPSS interpretation.

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.

Affected products

Mozilla Firefox — versions 115.37, 140.12
Mozilla Thunderbird — versions 140.12

Weakness classification (CWE)

CWE-119 — Improper Restriction of Operations within the Bounds of a Memory Buffer

References

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

Frequently asked questions

What is CVE-2026-12330?: CVE-2026-12330 is a medium-severity vulnerability in Mozilla Firefox, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 5.4/10. Published 2026-06-16.
How severe is CVE-2026-12330?: Medium severity. CVSS v3 base score is 5.4 out of 10.