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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (9.12%). 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 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.
- CVSS 3.1
- 8.8 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- EPSS
- 9.12% probability · 95th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-125, CWE-787
- Affected
- mozilla/firefox · mozilla/thunderbird
- Source
- security@mozilla.org
EPSS 9.1% since 26 October 2026; no change recorded yet. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=1966614Permissions 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
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.