Samba contains a flaw that may allow a malicious user to execute arbitrary shell commands. The issue is triggered due to MS-RPC does not properly check user-supplied input when passing RPC messages from external scripts to '/bin/sh'. It is possible that the flaw may allow code execution resulting in a loss of integrity.
Upgrade to version 3.0.25 or higher, as it has been reported to fix this vulnerability. In addition, Samba has released a patch for some older versions.