Memory safety bugs fixed in Firefox ESR 140.3, Thunderbird ESR 140.3, Firefox 143 and Thunderbird 143
21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 8.8epss 0.3%
exploitation probability
0.3%top 77% of all CVEs
observed exploitation
nono source reports it
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
References
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1938220%2C1980730%2C1981280%2C1981283%2C1984505%2C1985067https://lists.debian.org/debian-lts-announce/2025/09/msg00020.htmlhttps://lists.debian.org/debian-lts-announce/2025/09/msg00026.htmlhttps://www.mozilla.org/security/advisories/mfsa2025-73/https://www.mozilla.org/security/advisories/mfsa2025-75/https://www.mozilla.org/security/advisories/mfsa2025-77/https://www.mozilla.org/security/advisories/mfsa2025-78/