Out-of-bounds Read in Mozilla Firefox
CVE-2025-4918
An attacker was able to perform an out-of-bounds read or write on a JavaScript `Promise` object. 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
EPSS: 0.089 (94.7th percentile) — read the EPSS interpretation.
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.
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
- security@mozilla.org (Permissions Required)
- security@mozilla.org (Vendor Advisory)
- security@mozilla.org (Vendor Advisory)
- security@mozilla.org (Vendor Advisory)
- security@mozilla.org (Vendor Advisory)
- security@mozilla.org (Vendor Advisory)
- af854a3a-2127-422b-91ae-364da2661108
- af854a3a-2127-422b-91ae-364da2661108
- af854a3a-2127-422b-91ae-364da2661108 (Exploit, Third Party Advisory)
- af854a3a-2127-422b-91ae-364da2661108 (Exploit, Third Party Advisory)
Frequently asked questions
- What is CVE-2025-4918?
- CVE-2025-4918 is a critical-severity vulnerability in Mozilla Firefox, classified under Out-of-bounds Read. CVSS score: 9.8/10. Published 2025-05-17.
- How severe is CVE-2025-4918?
- Critical severity. CVSS v3 base score is 9.8 out of 10.
- Is CVE-2025-4918 known to be exploited?
- 5 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.