The info_generic function in xdg-mime looks like this:

info_generic()                                                                   
{                                                                                
    if mimetype --version >/dev/null 2>&1; then                                  
        DEBUG 1 "Running mimetype -b \"$1\""                                     
        mimetype -b "$1"                                                         
    else                                                                         
        DEBUG 1 "Running file --mime-type \"$1\""                                
        /usr/bin/file --mime-type "$1" 2> /dev/null | cut -d ":" -f 2 | sed s/"^ "//                                       
    fi                                                                           
                                                                                 
    if [ $? -eq 0 ]; then                                                        
        exit_success                                                             
    else                                                                         
        exit_failure_operation_failed                                            
    fi                                                                           
}

The problem occurs if /usr/bin/file is executed and the filename contains the colon.
Normally file outputs both the filename and the mimetype, but only the mimtype is desired so cut is employed to split the output from file into two pieces and return only the second, the mimetype.

I have not spent a lot of time trying to determine the best solution to this problem. What worked for me was to replace the whole line with:

        /usr/bin/file -b --mime-type "$1" 2> /dev/null

The -b option tell file to only output the mimetype and not the filename.