The bounded copy functions
strncat accept a size argument.
You should call these functions with a size argument that is derived from the size of the destination buffer.
Using a size argument that is derived from the source buffer may cause a buffer overflow.
Buffer overflows can lead to anything from a segmentation fault to a security vulnerability.
Check the highlighted function calls carefully. Ensure that the size parameter is derived from the size of the destination buffer, and not the source buffer.
This check is an approximation, so some results may not be actual defects in the program. It is not possible in general to compute the exact value of the variable without running the program with all possible input data.
The code below shows an example where
strncpy is called incorrectly, without checking the size of the destination buffer.
In the second example the call has been updated to include the size of the destination buffer.