Buffer overflow in Mozilla Firefox
CVE-2025-9187
Memory safety bugs present in Firefox 141 and Thunderbird 141. 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 142 and Thunderbird 142.
Vulnerability class: Buffer Overflow
Published · last modified .
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: 0.005 (38.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 38th percentile — 38.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · change: +0.000
Affected products
- Mozilla Firefox — versions 142
- Mozilla Thunderbird — versions 142
Weakness classification (CWE)
Public proof-of-concept exploits
References
- bugzilla.mozilla.org/buglist.cgi (Broken Link)
- www.mozilla.org/security/advisories/mfsa2025-64/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-70/ (Vendor Advisory)
Frequently asked questions
- What is CVE-2025-9187?
- CVE-2025-9187 is a critical-severity vulnerability in Mozilla Firefox, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 9.8/10. Published 2025-08-19.
- How severe is CVE-2025-9187?
- Critical severity. CVSS v3 base score is 9.8 out of 10.
- Is CVE-2025-9187 known to be exploited?
- 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.