It was found that provided string length arguments in four libcurl functions curl_escape(), curl_easy_escape(), curl_unescape and curl_easy_unescape were not properly checked and due to arithmetic in the functions, passing in the length 0xffffffff (2^32-1 or UINT_MAX or even just -1) would end up causing an allocation of zero bytes of heap memory that curl would attempt to write gigabytes of data into.
