Updated krb5 packages that improve client responsiveness and fix several security issues are now available for CentOS Linux 3.
Kerberos is a networked authentication system that uses a trusted third party (a KDC) to authenticate clients and servers to each other. Several double-free bugs were found in the Kerberos 5 KDC and libraries. A remote attacker could potentially exploit these flaws to execuate arbitrary code. The Common Vulnerabilities and Exposures project (cve.mitre.org) has assigned the names CAN-2004-0642 and CAN-2004-0643 to these issues. A double-free bug was also found in the krb524 server (CAN-2004-0772), however this issue does not affect CentOS Linux 3 Kerberos packages. An infinite loop bug was found in the Kerberos 5 ASN.1 decoder library. A remote attacker may be able to trigger this flaw and cause a denial of service. The Common Vulnerabilities and Exposures project (cve.mitre.org) has assigned the name CAN-2004-0644 to this issue. When attempting to contact a KDC, the Kerberos libraries will iterate through the list of configured servers, attempting to contact each in turn. If one of the servers becomes unresponsive, the client will time out and contact the next configured server. When the library attempts to contact the next KDC, the entire process is repeated. For applications which must contact a KDC several times, the accumulated time spent waiting can become significant. This update modifies the libraries, notes which server for a given realm last responded to a request, and attempts to contact that server first before contacting any of the other configured servers. All users of krb5 should upgrade to these updated packages, which contain backported security patches to resolve these issues.