GEN:SID 1:446
Message ICMP SKIP undefined code
Summary This event is generated when an ICMP "SKIP" message is generated with a non-zero ICMP code.
Impact Informational. This may indicate that the ICMP message has been crafted.
Detailed Information An ICMP "SKIP" message is issued when a SKIP request to provide keying material fails. The ICMP code value for this message should be 0.  If a non-zero code 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 "SKIP" 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 None.
Additional References