Firefox’s Content Processes component contains a use‑after‑free bug in the DOM that can lead to a sandbox escape. This flaw arises from improper memory deallocation and subsequent reuse. Based on the description, the escape could potentially allow an attacker to break isolation between content processes and the rest of the system, effectively raising privileges within the browser context.

The vulnerability is present in Mozilla Firefox releases prior to ESR 153.4, Firefox 157, ESR 115.42, and ESR 140.17, as well as in Mozilla Thunderbird releases prior to 157, 140.17, and 153.4. Users running these affected builds, or older ESR versions, are exposed, while any edition that includes one of the listed fix versions provides protection.

The CVSS score is 9.6, indicating a critical severity, and the EPSS score is less than 1%, implying a very low probability of exploitation at this time. The vulnerability is not listed in the CISA KEV catalog, so no active exploitation campaigns are publicly known. Attackers would need to trigger the use‑after‑free condition, likely via crafted web content, but the exact attack vector is not supplied in the data.