CVE-2026-124864 is a critical use-after-free vulnerability in the DOM Service Workers component of Firefox that allows sandbox escape. This flaw was addressed and fixed in Firefox 160 and Firefox ESR versions 115.45 and 153.7. The vulnerability has a high CVSS score of 9.6, indicating it can be exploited remotely without privileges and can lead to complete compromise of confidentiality, integrity, and availability. No known exploits in the wild have been reported. Users are advised to update to the fixed versions to mitigate the risk.