The content layout component in Mozilla Firefox 3.0 and 3.0.1 allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via a crafted but well-formed web page that contains "a simple set of legitimate HTML tags."
Improper Input Validation The product receives input or data, but it does
not validate or incorrectly validates that the input has the
properties that are required to process the data safely and
correctly.