CVE-2025-9181 is a vulnerability involving uninitialized memory in the JavaScript Engine component of Firefox and Thunderbird. It affects Firefox versions prior to 142 and ESR versions prior to 128.14 and 140.2, as well as corresponding Thunderbird versions. The issue was addressed in Firefox 142 and Firefox ESR 128.14. The vulnerability has a moderate impact rating and a CVSS score of 6.5, indicating a medium severity level. No known exploits in the wild have been reported.