CVE-2026-12314 is a memory safety bug affecting Mozilla Firefox and Thunderbird prior to versions Firefox 152 and Firefox ESR 140.12, and Thunderbird 152 and Thunderbird ESR 140.12. This vulnerability is part of a set of memory safety issues fixed in these releases, some of which showed evidence of memory corruption and could potentially be exploited to run arbitrary code. The vulnerability is classified under multiple CWEs related to memory safety (CWE-119, CWE-416, CWE-787, CWE-125). Mozilla has published official security advisories MFSA2026-57 and MFSA2026-58 detailing these fixes. The CVSS v3.1 base score is 7.5 with vector AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N, indicating network attack vector, low attack complexity, no privileges or user interaction required, unchanged scope, and high confidentiality impact without integrity or availability impact. No known exploits have been reported in the wild. The vendor advisories confirm that the vulnerability is fixed in Firefox 152 and Firefox ESR 140.12.

The vulnerability allows an attacker to potentially cause memory corruption which could lead to unauthorized disclosure of information (high confidentiality impact). There is no reported impact on integrity or availability. The CVSS score of 7.5 reflects a high severity due to the potential confidentiality breach. No known exploits in the wild have been reported, reducing immediate risk but the vulnerability remains critical to patch.

Mozilla has released official fixes for this vulnerability in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird ESR 140.12. Users and administrators should update affected products to these versions or later to remediate the vulnerability. Since this is not a cloud service, remediation depends on applying these updates. Patch status is confirmed by Mozilla advisories MFSA2026-57 and MFSA2026-58. No additional mitigation is required beyond applying the official updates.