curl_unescape() did not stop at the set length properly when %-codes were

used

lib/escape.c

@@ -100,7 +100,7 @@ char *curl_unescape(char *string, int length)
                             the "query part" where '+' should become ' '.
                             RFC 2316, section 3.10 */
   
-   while(--alloc) {
+   while(--alloc > 0) {
       in = *string;
       if(querypart && ('+' == in))
          in = ' ';
@@ -113,6 +113,7 @@ char *curl_unescape(char *string, int length)
         if(sscanf(string+1, "%02X", &hex)) {
           in = hex;
           string+=2;
+          alloc-=2;
         }
       }