GEN:SID 1:450
Message ICMP Time-To-Live Exceeded in Transit undefined code
Summary This event is generated when an ICMP "Time Exceeded" message is generated that has an invalid ICMP code.  
Impact Informational.  This may indicate that the ICMP message has been crafted.
Detailed Information An ICMP "Time Exceeded" message is issued when either the maximum number of hops has been exceeded or a timer has expired before all fragments have been received.  The ICMP code value for this message should be 0 or 1.  If a value of greater than 1 for the ICMP code is observed, it may be an indication that the packet was crafted with an invalid value.
Affected Systems This traffic should have no adverse impact.
Attack Scenarios An attacker may craft an ICMP "Time Exceeded" message with an invalid ICMP code.  A single packet itself is not harmful, but the unusual ICMP code may indicate that this packet was abnormally generated.
Ease of Attack Simple. There are many packages available to generate ICMP messages.
Corrective Action If a host or device in your network is generating this message, investigate why it does not have a standard ICMP code.
Additional References