Multiple SSH2 servers and clients do not properly handle strings with null characters in them when the string length is specified by a length field, which could allow remote attackers to cause a denial of service or possibly execute arbitrary code due to interactions with the use of null-terminated strings as implemented using languages such as C, as demonstrated by the SSHredder SSH protocol test suite.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A5797
http://www.cert.org/advisories/CA-2002-36.html
http://securitytracker.com/id?1005813
http://securitytracker.com/id?1005812
http://archives.neohapsis.com/archives/vulnwatch/2002-q4/0110.html