Null pointer dereference

[bird8693]

Enviroment

operating system: ubuntu18.04
compile command: make
test command: ./run_tests  poc

poc:

https://drive.google.com/open?id=1233VnpgxQZq0nUbKLXEOEYb5NcOPs--P

vulnerability description:

First observe the stack traceback, as shown in the figure:

It is a problem with CTinyJS :: term. On the TinyJS.cpp + 1737 line, a null pointer reference is triggered, as shown in the figure:

The reason for the vulnerability is that when the temporary assignment variable b is generated, it is not verified whether b is empty, and then b-> var refers to b, which causes the vulnerability.