Some vulnerabilities have been reported in Kerberos, which can be exploited by malicious people to disclose potentially sensitive information, cause a DoS (Denial of Service), or potentially compromise a vulnerable system.

1) The problem is that KDC uses a global variable for all incoming krb4 requests, but sets the variable only for certain requests. This can be exploited to crash an affected server, potentially execute arbitrary code, or disclose potentially sensitive memory.

2) An error exists in KDC when sending responses for krb4 requests. This can be exploited to disclose potentially sensitive stack memory via a specially crafted krb4 request.

Successful exploitation of the vulnerabilities requires that krb4 support is enabled in KDC (disabled by default in newer versions).

3) Two errors exist in the Kerberos RPC library when handling open file descriptors. This can be exploited to cause a memory corruption via an overly large number of RPC connections.

Successful exploitation of the vulnerability may allow execution of arbitrary code, but requires that the operating system allows an overly large number of opened file descriptors, and that "FD_SETSIZE" is not defined in the system headers for versions prior to 1.3.

Vulnerabilities #1 and #2 are reported in Kerberos 5 versions 1.6.3 and prior. Vulnerability #3 is reported in Kerberos 5 versions 1.2.2 through 1.3, and versions 1.4 through 1.6.3.

Solution
Apply vendor patches.
Further details available in Customer Area

Provided and/or discovered by
1) Reported by the vendor.
2) The vendor credits Jeff Altman of Secure Endpoints, and Red Hat Security Response Team.

Original Advisory
http://web.mit.edu/kerberos/www/advisories/MITKRB5-SA-2008-001.txt
http://web.mit.edu/kerberos/www/advisories/MITKRB5-SA-2008-002.txt

Other references
Further details available in Customer Area

Deep Links
Links available in Customer Area