HTTP Compliance Exception

It seems to be a global setting. I couldn't find a way within the configuration utility to make an exception. But you could use an iRule to create an exception. See the iRule below.

when ASM_REQUEST_DONE {
  set uri [HTTP::uri]
  foreach violation [ASM::violation names] {
      if { $uri starts_with "/login.php" && [ASM::violation count] < 2 } {
          if { [matchclass [ASM::violation attack_types] equals "ATTACK_TYPE_HTTP_REQUEST_SMUGGLING_ATTACK"] } {
              log local0. "Violation $violation detected for URI $uri, but allowed anyway."
              ASM::unblock
          }
      } else {
          # More than one violation, too dangerous to Unblock
          return
      }
  }
}