The CSS border-rendering code in Mozilla Firefox and Thunderbird 1.x before 1.5 and 1.0.x before 1.0.8, Mozilla Suite before 1.7.13, and SeaMonkey before 1.0 allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via certain Cascading Style Sheets (CSS) that causes an out-of-bounds array write and buffer overflow.