What is CVE-2025-0247?

CVE-2025-0247 is a critical-severity vulnerability in Mozilla Firefox, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2025-01-07.

How severe is CVE-2025-0247?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Buffer overflow in Mozilla Firefox

CVE-2025-0247

Memory safety bugs present in Firefox 133 and Thunderbird 133. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 134 and Thunderbird 134.

Vulnerability class: Buffer Overflow

Published 2025-01-07 · last modified 2026-10-05.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.093 (95.2th percentile), scored 2026-10-08.

Low probability of exploitation in the next 30 days, but still tracked. 95th percentile — 95.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.093 · newest: 0.093 · change: -0.001

Affected products

Mozilla Firefox — versions 134
Mozilla Thunderbird — versions 134

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

bugzilla.mozilla.org/buglist.cgi (Issue Tracking, Broken Link)
www.mozilla.org/security/advisories/mfsa2025-01/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2025-04/ (Vendor Advisory)

Frequently asked questions

What is CVE-2025-0247?: CVE-2025-0247 is a critical-severity vulnerability in Mozilla Firefox, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2025-01-07.
How severe is CVE-2025-0247?: Critical severity. CVSS v3 base score is 9.8 out of 10.