Access of Resource Using Incompatible Type ('Type Confusion')
The type inference system allows the compilation of functions that can cause type confusions between arbitrary objects when compiled through the IonMonkey just-in-time (JIT) compiler and when the constructor function is entered through on-stack replacement (OSR). This allows for possible arbitrary reading and writing of objects during an exploitable crash. This vulnerability affects Thunderbird < 60.6, Firefox ESR < 60.6, and Firefox < 66.
CWE-843 - Access of Resource Using Incompatible Type ('Type Confusion')
The program allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.