Memory safety bugs present in Firefox ESR 140.2, Thunderbird ESR 140.2, Firefox 142 and Thunderbird 142. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 143, Firefox ESR 140.3, Thunderbird 143, and Thunderbird 140.3.
Fix
Patch, vendor advisory and mitigation references on NVD 4
- https://www.mozilla.org/security/advisories/mfsa2025-73/ Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2025-75/ Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2025-77/ Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2025-78/ Vendor Advisory
Every line above is quoted from NVD, CISA, Microsoft, the vendor's own advisory or DISA; nothing is generated.
Change history 1
- First seenCVSS 8.8 · mozillaNVD modified 2026-10-18 21:10
Affected (CPE criteria) 4
cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*
References 7
- https://bugzilla.mozilla.org/buglist.cgi?bug_id=1938220%2C1980730%2C1981280%2C1981283%2C1984505%2C1985067 Issue Tracking
- https://www.mozilla.org/security/advisories/mfsa2025-73/ Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2025-75/ Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2025-77/ Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2025-78/ Vendor Advisory
- https://lists.debian.org/debian-lts-announce/2025/09/msg00020.html
- https://lists.debian.org/debian-lts-announce/2025/09/msg00026.html