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.
Affected products
mozilla: firefox; mozilla: thunderbird
References8
- 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
- bugzilla.mozilla.org/show_bug.cgi?id=1966614 Permissions Required
- lists.debian.org/debian-lts-announce/2025/05/msg00024.html
- lists.debian.org/debian-lts-announce/2025/05/msg00046.html
Metrics
- CVSS 3.1
-
8.8
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H - EPSS — exploit probability
- 9% percentile: 95 · as of 7 November 2026
- CWE
- CWE-125CWE-787
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.