The Graphics: CanvasWebGL component in Mozilla applications implements incorrect boundary checks, resulting in a buffer overflow flaw classified as CWE‑120. By manipulating WebGL input, an attacker can trigger the exploit to execute arbitrary code with the privileges of the browser process, enabling local privilege escalation within the affected application.

Mozilla Firefox and Mozilla Thunderbird are affected. In Firefox, all releases prior to version 156 and ESR releases below 115.41, 140.16, and 153.3 are vulnerable. In Thunderbird, all releases before 156 and ESR releases below 140.16 are at risk.

The CVSS score of 8.8 indicates a high severity. The EPSS score of < 1% indicates the probability of exploitation is very low but still non-zero, and the vulnerability is not listed in the CISA KEV catalog, implying no known widespread exploitation. The likely attack vector is the execution of malicious WebGL content served by a web page or email, requiring user interaction to load the content. If exploited, the attacker can gain elevated privileges within the browser process, potentially affecting the host operating system when the browser runs with elevated rights.