Blocking HTTP Error 500 using F5 ASM

you can do this without using ASM module. By using Irule either you can redirect to any other application page or send custom response in case of 500 RespCode.

Redirect to error Page.

when HTTP_RESPONSE {
    if {  [HTTP::status] eq "500" } {
    HTTP::redirect "www.abc.com/error.html" }
}

Send Custom Response

when HTTP_RESPONSE {
if {  [HTTP::status] eq "500" } {
        HTTP::respond 200 content {
        
            
            Error
        
            
                Please contact support.
            
            
        }
    }
}