CVE-2026-12308 is a memory safety bug in Mozilla Firefox identified and fixed in Firefox 152 and Firefox ESR 140.12. This vulnerability is one among multiple memory safety issues addressed in these releases, some of which had evidence of memory corruption that could potentially be exploited to execute arbitrary code. The fixes are included in the official Mozilla security advisories MFSA 2026-57 and MFSA 2026-58. No detailed CVSS score is provided, but the impact is considered moderate based on Mozilla's assessment. The vulnerability affects Firefox versions before 152 and Firefox ESR versions before 140.12.

The vulnerability involves memory safety issues that could lead to memory corruption. While no active exploitation has been reported, such bugs can potentially be leveraged to execute arbitrary code or cause other security impacts. Mozilla classifies the impact of this specific vulnerability as moderate, within a set of related memory safety bugs with varying severity from low to high.

Mozilla has released official fixes for this vulnerability in Firefox 152 and Firefox ESR 140.12. Users and administrators should update affected Firefox installations to these versions or later to remediate the issue. No additional mitigation actions are required beyond applying the official updates.