The vulnerability is a use‑after‑free in Firefox’s DOM Content Processes component that allows a sandbox escape. When a freed object is still accessed, malformed or malicious input can corrupt memory, enabling execution of code outside the browser’s sandbox. An attacker can thus bypass isolation and potentially compromise the entire host system. The issue has been fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, Firefox ESR 140.17, Thunderbird 140.17, Thunderbird 153.4, and Thunderbird 157.

This vulnerability affects all Mozilla Firefox releases older than Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17, as well as all Thunderbird releases older than Thunderbird 140.17, Thunderbird 153.4, and Thunderbird 157.

The EPSS score is < 1%, indicating a very low but nonzero probability that this vulnerability has been exploited in the wild. The CVSS score of 9.6 indicates a high severity, and the vulnerability is not listed in CISA KEV. The nature of a use‑after‑free leading to sandbox escape (CWE‑416) combined with potential arbitrary memory writes (CWE‑825) suggests a high potential impact. The likely attack vector is through crafted web content or malicious extensions that can trigger the error in a content process.