MITRE description:

Multiple off-by-one errors in the cURL library (libcurl) 7.11.2 through 7.15.0 allow local users to trigger a buffer overflow and cause a denial of service or bypass PHP security restrictions via certain URLs that (1) are malformed in a way that prevents a terminating null byte from being added to either a hostname or path buffer, or (2) contain a "?"  separator in the hostname portion, which causes a "/" to be prepended to the resulting string.