Description
There was a way to change the value of JavaScript Object properties that were supposed to be non-writeable. This vulnerability was fixed in Firefox 144, Firefox ESR 115.29, Firefox ESR 140.4, Thunderbird 144, and Thunderbird 140.4.
Affected products
mozilla: firefox; mozilla: thunderbird
References8
- www.mozilla.org/security/advisories/mfsa2025-81/ Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2025-82/ Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2025-83/ Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2025-84/ Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2025-85/ Vendor Advisory
- bugzilla.mozilla.org/show_bug.cgi?id=1989978 Issue TrackingPermissions Required
- lists.debian.org/debian-lts-announce/2025/10/msg00015.html
- lists.debian.org/debian-lts-announce/2025/10/msg00031.html
Metrics
- CVSS 3.1
-
6.5
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N - EPSS — exploit probability
- 0% percentile: 14 · as of 9 November 2026
- CWE
- CWE-591
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.