Out-of-bounds Read in Mozilla Firefox
CVE-2025-4919
An attacker was able to perform an out-of-bounds read or write on a JavaScript object by confusing array index sizes. This vulnerability was fixed in Firefox 138.0.4, Firefox ESR 128.10.1, Firefox ESR 115.23.1, Thunderbird 128.10.2, and Thunderbird 138.0.2.
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: 0.086 (95.0th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 95th percentile — 95.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.086 · newest: 0.086 · change: 0.000
Affected products
- Mozilla Firefox — versions 115.23.1, 128.10.1, 138.0.4
- Mozilla Thunderbird — versions 128.10.2, 138.0.2
Weakness classification (CWE)
Public proof-of-concept exploits
References
- bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
- www.mozilla.org/security/advisories/mfsa2025-36/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-37/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-38/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-40/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-41/ (Vendor Advisory)
- af854a3a-2127-422b-91ae-364da2661108
- af854a3a-2127-422b-91ae-364da2661108
Frequently asked questions
- What is CVE-2025-4919?
- CVE-2025-4919 is a high-severity vulnerability in Mozilla Firefox, classified under Out-of-bounds Read. CVSS score: 8.8/10. Published 2025-05-17.
- How severe is CVE-2025-4919?
- High severity. CVSS v3 base score is 8.8 out of 10.
- Is CVE-2025-4919 known to be exploited?
- 5 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.