unrealircd: multiple vulnerabilities

Multiple vulnerabilities have been reported in UnrealIRCd:

* The vendor reported a buffer overflow in the user authorization code.

* The vendor reported that the distributed source code of UnrealIRCd was compromised and altered to include a system() call that could be called with arbitrary user input.

A remote attacker could exploit these vulnerabilities to cause the execution of arbitrary commands with the privileges of the user running UnrealIRCd, or a Denial of Service condition.