An integer overflow in the Graphics: Text component allows an attacker to supply crafted content that can corrupt memory during text rendering. This flaw can lead to the execution of arbitrary code or cause the application to crash, denying service. The weakness is a classic integer overflow (CWE‑190) affecting how the bounds of a text buffer are calculated, potentially creating a vulnerability where the code runs with the privileges of the application.

The vulnerability affects Mozilla Firefox, including the main and ESR releases, as well as Mozilla Thunderbird. The affected versions are those prior to Firefox 149.0.2 and Firefox ESR 140.9.1, and prior to Thunderbird 149.0.2 and Thunderbird 140.9.1. Users running older releases of these browsers are at risk.

The CVSS score of 8.8 indicates high severity, and the EPSS score of less than 1% suggests a low current exploitation probability. The vulnerability is not listed in the CISA KEV catalog. Likely exploitation would involve an attacker delivering malicious content—such as a specially crafted webpage or mail—rendered by the affected browser or mail client, triggering the integer overflow during text drawing. Without official exploitation evidence, the exact attack vector is inferred based on the component description.