Use After Free
The mozilla::dom::TextTrack::AddCue function in Mozilla Firefox before 29.0 and SeaMonkey before 2.26 does not properly perform garbage collection for Text Track Manager variables, which allows remote attackers to execute arbitrary code or cause a denial of service (use-after-free and heap memory corruption) via a crafted VIDEO element in an HTML document.
CWE-416 - Use After Free
Use-after-free (UaF) vulnerability occurs when the application is using a pointer to memory that has been freed. Any attempt to read/write to a buffer after it is de-allocated allows memory corruption, sensitive information exposure, and can potentially lead to arbitrary code execution.