Buffer overflow in Mozilla Firefox
CVE-2025-8040
Memory safety bugs present in Firefox ESR 140.0, Thunderbird ESR 140.0, Firefox 140 and Thunderbird 140. 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 141, Firefox ESR 140.1, Thunderbird 141, and Thunderbird 140.1.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.003 (23.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 23rd percentile — 23.1% 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 140.1, 141
- Mozilla Thunderbird — versions 140.1, 141
Weakness classification (CWE)
Public proof-of-concept exploits
References
- bugzilla.mozilla.org/buglist.cgi
- www.mozilla.org/security/advisories/mfsa2025-56/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-59/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-61/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-63/ (Vendor Advisory)
Frequently asked questions
- What is CVE-2025-8040?
- CVE-2025-8040 is a high-severity vulnerability in Mozilla Firefox, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 8.8/10. Published 2025-07-22.
- How severe is CVE-2025-8040?
- High severity. CVSS v3 base score is 8.8 out of 10.
- Is CVE-2025-8040 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.