The MIT krb5 Key Distribution Center (KDC) implementation can corrupt the heap by attempting to free memory at a random address when it receives a certain unlikely (but valid) request via a TCP connection. This attempt to free unallocated memory can result in a KDC crash and consequent denial of service. [CAN-2005-1174] Additionally, the same request, when received by the KDC via either TCP or UDP, can trigger a bug in the krb5 library which results in a single-byte overflow of a heap buffer. Additionally, application servers are vulnerable to a highly improbable attack, provided that the attacker controls a realm sharing a cross-realm key with the target realm. [CAN-2005-1175] An unauthenticated attacker may be able to use these vulnerabilities to execute arbitrary code on the KDC host, potentially compromising an entire Kerberos realm. No exploit code is known to exist at this time. Exploitation of these vulnerabilities is believed to be difficult.
Nalin, It seems CAN-2005-1174 sin't going to affect RHEL2.1 or RHEL3, can you verify this? CAN-2005-1175 should affect RHEL2.1, RHEL3, and RHEL4
I can confirm that CAN-2005-1174 shouldn't affect RHEL 2.1 or 3. Both releases include krb5 1.2.x, which predates the TCP code. (The variable in question is there, but the code path which leads to it being mistakenly passed to free() before it's initialized isn't.)
According to MIT, in order to exploit CAN-2005-1175 the attacker must control a realm sharing a cross-realm key with the target realm. I'm lowering the severity to "moderate" for that particular issue.
public, removing embargo http://web.mit.edu/kerberos/www/advisories/
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on the solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2005-567.html