Description
Memory safety bug present in Firefox ESR 128.9, and Thunderbird 128.9. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox ESR 128.10 and Thunderbird 128.10.
Affected products
mozilla: firefox; mozilla: thunderbird
References4
- www.mozilla.org/security/advisories/mfsa2025-29/ Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2025-32/ Vendor Advisory
- bugzilla.mozilla.org/show_bug.cgi?id=1894100 Permissions Required
- lists.debian.org/debian-lts-announce/2025/05/msg00024.html
Metrics
- CVSS 3.1
-
8.1
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H - EPSS — exploit probability
- 0% percentile: 42 · as of 7 November 2026
- CWE
- CWE-119
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.