Updated krb5 packages that fix multiple security issues are now available
for Red Hat Enterprise Linux 4.
This update has been rated as having important security impact by the Red
Hat Security Response Team.
Kerberos is a networked authentication system that uses a trusted third
party (a KDC) to authenticate clients and servers to each other.
A double-free flaw was found in the krb5_recvauth() routine which may be
triggered by a remote unauthenticated attacker. Red Hat Enterprise Linux 4
contains checks within glibc that detect double-free flaws. Therefore, on
Red Hat Enterprise Linux 4 successful exploitation of this issue can only
lead to a denial of service (KDC crash). The Common Vulnerabilities and
Exposures project assigned the name CAN-2005-1689 to this issue.
Daniel Wachdorf discovered a single byte heap overflow in the
krb5_unparse_name() function, part of krb5-libs. Sucessful exploitation of
this flaw would lead to a denial of service (crash). To trigger this flaw
an attacker would need to have control of a kerberos realm that shares a
cross-realm key with the target, making exploitation of this flaw unlikely.
Daniel Wachdorf also discovered that in error conditions that may occur in
response to correctly-formatted client requests, the Kerberos 5 KDC may
attempt to free uninitialized memory. This could allow a remote attacker
to cause a denial of service (KDC crash) (CAN-2005-1174).
Gael Delalleau discovered an information disclosure issue in the way
some telnet clients handle messages from a server. An attacker could
construct a malicious telnet server that collects information from the
environment of any victim who connects to it using the Kerberos-aware
telnet client (CAN-2005-0488).
The rcp protocol allows a server to instruct a client to write to arbitrary
files outside of the current directory. This could potentially cause a
security issue if a user uses the Kerberos-aware rcp to copy files from a
malicious server (CAN-2004-0175).
All users of krb5 should update to these erratum packages, which contain
backported patches to correct these issues. Red Hat would like to thank
the MIT Kerberos Development Team for their responsible disclosure of these