What is CVE-2025-4092?

CVE-2025-4092 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 2025-04-29.

How severe is CVE-2025-4092?

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

Buffer overflow in Mozilla Firefox

CVE-2025-4092

Memory safety bugs present in Firefox 137 and Thunderbird 137. 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 138 and Thunderbird 138.

Vulnerability class: Buffer Overflow

Published 2025-04-29 · last modified 2026-09-30.

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:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.003 (21.1th percentile), scored 2026-10-04.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 21st percentile — 21.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: +0.000

Affected products

Mozilla Firefox — versions 138
Mozilla Thunderbird — versions 138

Weakness classification (CWE)

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

References

bugzilla.mozilla.org/buglist.cgi (Broken Link)
www.mozilla.org/security/advisories/mfsa2025-28/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2025-31/ (Vendor Advisory)

Frequently asked questions

What is CVE-2025-4092?: CVE-2025-4092 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 2025-04-29.
How severe is CVE-2025-4092?: Medium severity. CVSS v3 base score is 6.5 out of 10.