1. A cookie is set using the secure keyword for https://target 2. curl is redirected to or otherwise made to speak with http://target (same hostname, but using clear text HTTP) using the same cookie set 3. The same cookie name is set - but with just a slash as path (path=\"/\",).

Since this site is not secure, the cookie should just be ignored. 4. A bug in the path comparison logic makes curl read outside a heap buffer boundary The bug either causes a crash or it potentially makes the comparison come to the wrong conclusion and lets the clear-text site override the contents of the secure cookie, contrary to expectations and depending on the memory contents immediately following the single-byte allocation that holds the path. The presumed and correct behavior would be to plainly ignore the second set of the cookie since it was already set as secure on a secure host so overriding it on an insecure host should not be okay.