What is CVE-2026-6764?

CVE-2026-6764 is a medium-severity vulnerability in Mozilla Firefox, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 6.5/10. Published 2026-04-21.

How severe is CVE-2026-6764?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Buffer overflow in Mozilla Firefox

CVE-2026-6764

Incorrect boundary conditions in the DOM: Device Interfaces component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.

Vulnerability class: Buffer Overflow

Published 2026-04-21 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L.

EPSS exploit prediction

EPSS: 0.004 (31.1th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 31st percentile — 31.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

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

Affected products

Mozilla Firefox — versions 140.10, 150
Mozilla Thunderbird — versions 140.10, 150

Weakness classification (CWE)

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

References

bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
www.mozilla.org/security/advisories/mfsa2026-30/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2026-32/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2026-33/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2026-34/ (Vendor Advisory)

Frequently asked questions

What is CVE-2026-6764?: CVE-2026-6764 is a medium-severity vulnerability in Mozilla Firefox, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 6.5/10. Published 2026-04-21.
How severe is CVE-2026-6764?: Medium severity. CVSS v3 base score is 6.5 out of 10.