CVE-2025-4918
Out-of-bounds access when resolving Promise objects
CRITICAL 9.8EPSS 9.4%
An attacker was able to perform an out-of-bounds read or write on a JavaScript `Promise` object. This vulnerability affects Firefox < 138.0.4, Firefox ESR < 128.10.1, Firefox ESR < 115.23.1, Thunderbird < 128.10.2, and Thunderbird < 138.0.2.
- Affected
- Mozilla · Firefox · Thunderbird
- CVSS v3.1 CNA
- 9.8 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - EPSS
- 9.43% chance of exploitation in the next 30 days, 95th percentile
- Published
- 2025-05-17
- Updated
- 2026-04-13
Proof-of-concept exploits (2)
- https://www.vicarius.io/vsociety/posts/cve-2025-4918-detect-firefox-out-of-bounds-write
- https://www.vicarius.io/vsociety/posts/cve-2025-4918-mitigate-firefox-out-of-bounds-write
Security advisories
- https://www.mozilla.org/security/advisories/mfsa2025-36
- https://www.mozilla.org/security/advisories/mfsa2025-37
- https://www.mozilla.org/security/advisories/mfsa2025-38
- https://www.mozilla.org/security/advisories/mfsa2025-40
- https://www.mozilla.org/security/advisories/mfsa2025-41