VulnerabilityModified
CVE-2025-4918
An attacker was able to perform an out-of-bounds read or write on a JavaScript `Promise` object.
CRITICAL 9.8EPSS 9.46%
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (9.46%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
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.
- CVSS 3.1
- 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 9.46% probability · 95th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-125, CWE-787
- Affected
- mozilla/firefox · mozilla/thunderbird
- Source
- security@mozilla.org
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=1966612Permissions Required
- https://www.mozilla.org/security/advisories/mfsa2025-36/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2025-37/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2025-38/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2025-40/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2025-41/Vendor Advisory
- https://lists.debian.org/debian-lts-announce/2025/05/msg00024.html
- https://lists.debian.org/debian-lts-announce/2025/05/msg00046.html
- https://www.vicarius.io/vsociety/posts/cve-2025-4918-detect-firefox-out-of-bounds-writeExploit, Third Party Advisory
- https://www.vicarius.io/vsociety/posts/cve-2025-4918-mitigate-firefox-out-of-bounds-writeExploit, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.