fill_mishblk() does not check the length of the read buffer, and copy 0xCC bytes from it. The length of the buffer is controlled by an attacker. By providing a length smaller than 0xCC, memcpy reaches out of the malloc'ed bound.
This possibly leads to memory layout information leaking in the data. This might be used in a chain of vulnerability in order to reach code execution.

```
185 void fill_mishblk(char* c, struct _mishblk* m)
186 {
187     memset(m, 0, sizeof(struct _mishblk));
188     memcpy(m, c, 0xCC);
```
In the above code, the memory allocated for `c` may be shorter than 0xCC bytes.

Upstream bug report :
https://github.com/Lekensteyn/dmg2img/issues/11