What is CVE-2026-84126?

CVE-2026-84126 is a medium-severity vulnerability, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 4.3/10. Published 2026-09-01.

How severe is CVE-2026-84126?

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

CVE-2026-84126

CVE-2026-84126

Incorrect boundary conditions in the Layout: Grid component. This vulnerability was fixed in Firefox 155 and Thunderbird 155.

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.

Weakness classification (CWE)

CWE-120 — Buffer Copy without Checking Size of Input (Classic Buffer Overflow)

References

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

Frequently asked questions

What is CVE-2026-84126?: CVE-2026-84126 is a medium-severity vulnerability, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 4.3/10. Published 2026-09-01.
How severe is CVE-2026-84126?: Medium severity. CVSS v3 base score is 4.3 out of 10.