Let me try:
The claimed issue identifies a bug in curl that
1. only existed in debug-builds (thus disqualified)
2. even in debug-builds, a bad access will at worst cause a crash, which is also what assert itself does when triggered. Thus having the same end result. Not a vulnerability.
3. in most situations, the bad access will not cause any problems at all, even in debug-builds (because the accessed stack memory is readable)