The Netmonitor component contains a flaw that enables a local user to elevate privileges within the application, bypassing the intended security model. This can allow the attacker to perform actions normally restricted, potentially compromising data confidentiality, integrity, and availability inside the application.

Mozilla Firefox versions earlier than 148, Firefox ESR earlier than 140.8, Mozilla Thunderbird versions earlier than 148 and Thunderbird ESR earlier than 140.8 are affected.

The CVSS base score of 8.8 indicates high severity. The EPSS value of less than 1 % suggests exploitation is unlikely, and the vulnerability is not in the CISA Known Exploited Vulnerabilities catalog. Based on the fact that the flaw is in the Netmonitor component which runs locally on the user’s machine, the most likely attack vector is local, a user would need to run or manipulate the Netmonitor feature. The weakness corresponds to CWE‑269, improper privilege handling, allowing a privilege‑escalation event inside the application scope, and could potentially extend to the operating system if the application can affect privileged processes.