Multiple vulnerabilities have been reported in version five of the widely-used Kerberos authentication protocol. The most serious could be exploited by crackers to gain root control to authentication servers.

Exploits are yet to surface and patches are available. All releases of MIT Kerberos 5 up to and including krb5-1.3.4 are affected. At fault are "double-free vulnerabilities" in MIT Kerberos 5 implementation's Key Distribution Center (KDC) program and libraries. Double free vulnerabilities arise when programs try to free up the same portion of system memory twice, in this case creating a possible means for a remote attacker to execute arbitrary code on target systems.

Also, an error in the ASN.1 decoder of MIT Kerberos 5 could be used to cause vulnerable systems to hang. An attacker would be able to carry out this denial of service attack without first having to log onto vulnerable systems.

Developers are advised to update to version krb5-1.3.5, when it becomes available. In the meantime, MIT has published patches to address the vulnerability in earlier versions of its code. A summary of the products affected - along with responses from vendors - is here. Some users of Cisco VPN 3000 Series Concentrators will, for example, need to update their software .

Kerberos was developed by MIT and is a popular means for securely authenticating a request for a service in a computer network. The name derives from Greek mythology, where Cerberus is the three-headed dog guarding the gates of Hades. ®

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