Incorrect boundary conditions in Firefox’s layout engine for block and inline elements can cause improper memory access, potentially allowing an attacker to corrupt internal state and execute arbitrary code or crash the browser. The flaw maps to CWE‑119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) and CWE‑787 (Out‑of‑Bounds Write).

Mozilla Firefox browsers older than version 159.0.1 are affected. Any installation running a pre‑159.0.1 release may be vulnerable.

The CVSS score is 8.8 and the vulnerability is not listed in the CISA KEV catalog; an EPSS score is not available, so the precise risk level cannot be quantified. The likely attack vector is a crafted web page that triggers the layout engine’s boundary error; this inference is based on the description of memory corruption during rendering. The absence of exploitation evidence limits the ability to predict successful attacks, but the high severity score indicates that the flaw is serious if exploited.